One pawn, one tempo, one very fast centre
Quick answer: The Evans Gambit is 1.e4 e5 2.Nf3 Nc6 3.Bc4 Bc5 4.b4, offering a pawn to divert Black's bishop so White can play c3 and d4 and rip open the centre with tempo. It also opens lines for Ba3 or Qb3, hitting f7 and stopping Black from castling comfortably. Main line is 4...Bxb4 5.c3 Ba5.
This opening is nearly two hundred years old and it still wins games at club level, which tells you something.
It's named after William Davies Evans, a Welsh sea captain, and the first recorded game with it was Evans against McDonnell in London, 1827. Then it went out of fashion for most of a century as defensive technique improved, and came back partly because Kasparov played it at the top level in the 1990s and reminded everyone it was dangerous.
I've used it as a surprise weapon on and off for years, and I like it for a specific reason that has nothing to do with theory: it turns a quiet Italian Game into a sharp one on move four, before Black has had a chance to settle into a comfortable setup.
That timing is the underrated part. Most players who answer 1.e4 with e5 have a plan for the Italian, and that plan involves slow manoeuvring. Move four is early enough that they are still on autopilot, and autopilot against a gambit is how people end up a tempo down with an exposed king.
Why the pawn is worth it
The move 4.b4 looks like a random wing pawn offer. It isn't, and understanding the point makes the whole opening make sense.
Black's bishop on c5 is doing an important job. It controls d4, which is exactly the square White wants to occupy with a pawn to build a big centre.
So White offers the b4 pawn specifically to divert that bishop. If Black takes with 4...Bxb4, White plays 5.c3, hitting the bishop again with tempo. The bishop retreats, usually to a5, and now White plays d4 with a strong centre and a lead in development, having spent a pawn to buy it.
Three concrete things White gets:
A centre. Pawns on e4 and d4 with the c3 pawn supporting, which is the classical ideal.
Tempo. The c3 move that builds the centre also attacks the bishop, so White develops while Black retreats.
Diagonals. The b file and the a3-f8 diagonal open up. Ba3 can prevent Black castling kingside, and Qb3 hits f7, which is the weakest square in Black's camp before castling.
That last idea is worth internalising because it recurs across all the sharp e4 openings. The Fried Liver Attack targets exactly the same square by a different route, and once you see f7 as the target, a lot of Italian Game ideas stop feeling arbitrary.
The main lines
After 4.b4 Black has three practical choices.
4...Bxb4 (accepted) is the main line and the critical test. Play continues 5.c3 Ba5, which is the most common retreat, keeping the bishop active on the a5-e1 diagonal and eyeing c3. Then 6.d4 and White has what the gambit promised.
Black can also retreat 5...Bc5, going back where it came from, or 5...Be7, which is solid and passive. Both are playable and both give White a comfortable game with the pawn as the price.
4...Bb6 (declined) keeps the bishop on the a7-g1 diagonal without taking. Most analysts consider declining weaker than accepting and returning the pawn later, because Black concedes the space and tempo without gaining the material. White continues with a4 or b5 and just has a good position.
4...d5 is the counterattacking try, hitting the centre immediately rather than playing along. It's a legitimate response and it's the one I'd worry about most from a prepared opponent, because it changes the character of the game away from White's preparation.
There's a fourth response worth mentioning, which is 4...Nxb4. Taking with the knight rather than the bishop looks reasonable and is generally considered inferior, because it leaves the bishop on c5 where White wanted it gone, and the knight on b4 can be chased with c3 anyway. If your opponent plays it, you have effectively been given the tempo without paying for it, so proceed with c3 and d4 and be quietly pleased.
The Evans Gambit entry has the deeper theoretical branches. For practical purposes, knowing the accepted line to about move eight and understanding the ideas behind it covers the overwhelming majority of club games.
Traps that end games early
The Evans has a rich supply of ways for Black to lose quickly, which is a large part of its practical value.
The recurring theme is that Black gets greedy. Having won a pawn, there's a strong temptation to hold onto it and grab more, and the resulting lost tempi are exactly what White is playing for.
Watch for the moment Black's queen or bishop wanders to pick up material on the queenside while White is developing toward the king. That's the position where a sacrifice on f7 or a rapid Qb3 tends to be decisive.
The other common collapse is Black failing to castle. Ba3 makes kingside castling awkward, and a king stuck in the centre with the position opening is the standard way these games end.
I checked my own results with it out of curiosity before writing this. Small sample, but the pattern was clear enough: against opponents rated below me the score was excellent, and against stronger opponents who took the pawn and then played sensibly, it was a slow grind where I never quite proved compensation. That maps exactly onto what the theory says, which was reassuring and slightly deflating at the same time.
I'd caution against learning traps as your main preparation though. Traps work until they don't, and an opponent who knows the line leaves you a pawn down with nothing to show. The reason to play the Evans is the position it produces, not the tricks inside it.
What you should actually memorise is the plan: take on b4 or don't, either way White plays c3 and d4, develops quickly, and aims at f7 and the uncastled king. Drilling that sequence on the opening trainer until it's automatic is worth more than knowing five traps by name.
Does it hold up as you improve?
Honest answer: it holds up better than most romantic era gambits and worse than a mainline opening.
At club level, up to roughly 1800, it's genuinely strong. Most opponents don't know the accepted lines, they take the pawn because taking free pawns is a reflex, and they end up in a position where White's ideas are easy and Black's are hard. Easy positions win games.
Above that, prepared opponents know the defensive setups and the objective evaluation is that Black is fine with accurate play. You're then playing for practical chances rather than an advantage, which is a legitimate choice but you should know that's what you're doing.
Kasparov's revival is instructive here. He used it as a surprise weapon, not a main system, and that's the right frame. It's excellent when your opponent hasn't prepared for it and merely playable when they have.
If you're building a repertoire around 1.e4 e5, I'd have it as a second option alongside the main Italian rather than as your only line. That way you choose when to sharpen the game. The repertoire guide for 1200 to 1500 makes the case for breadth over depth at that level, and the Evans fits neatly as the aggressive alternative when you want one.