GURPS combat is probably similar to any other combat system you've seen.
A fight is broken up into turns, which are each about a second long. During each turn you get one Maneuver. These could be Attack, All-Out Attack, Feint, Concentrate, Ready, or something else.
During an Attack Maneuver, the attacker rolls his weapon skill (which could be a technique). If he succeeds at this roll, he has potentially hit. The defender gets to make a defense roll (one of parry, block, or dodge). If the defender succeeds, he takes no damage. If the attacker critically succeeds at his roll, the defender gets no defense roll and the attacker may get increased damage.
That's the basic combat mechanics. The rest is details.
### Feint
If the attacker chooses, he rolls a contest between his skill and the defender's best combat skill. If the attacker wins the contest, in the following turn, the attacker attacks again. but this time his margin of victory / 2 is subtracted from the defenders defense roll.
### Deceptive Attack
Similar to a feint, an attacker might choose to subtract X from his attack, and also subtract X/2 from the defender's defense roll.
### All-Out Attack
This is an attack that you invest everything into it. You cannot use any defense here. Two ways this can happen: 2 attacks or +2 damage for a single attack.
### All-Out Defense
Two defenses and no attacks.
## Defenses
**Dodge** is a motion that moves you out of the way of an attack.
**Parry** is a motion with your weapon to move the opponent's weapon out of line.
**Block** is using a shield to block an attack.