Gaelic football is played with 15 players on the field from each team at a time. The full squads may consist of as many as 25-30 players.
As the game starts, most teams employ the regular system of six defenders, two midfielders, six attackers and a goalkeeper. There are two lines of defenders and two lines of attackers. Each line consists of three.
As you can see below, those closest to the goalkeeper are ”full backs” then those in front are ”half backs”. They will match up with the full forwards and half forwards of the other team respectively. It will look like the below image.
The game of Gaelic Football is a tactical one, however it is not played strictly positionally like soccer or rugby. It is a man vs opponent game. each back will mark or ”stick with” the forward in their opposing position for as long as the game goes on. Backs are told to track their men wherever they run, and as I have mentioned before the field is much larger than that of soccer or football and there are no limits on where any player can go. The goalkeepers themselves can go anywhere on the field. Some at the top level take free kicks for their teams at the other end of the field, then have to run back to the goal.
As a side not, you get free kicks in Gaelic for anything deemed unreasonable, a closed fist hit, a pull of a jersey, a trip, a kick, or handling the ball while it is on the ground. The way you must pik a ball up is by scooping it with your toe. If your foot does not slide under the ball as you pick it up you will concede a free kick. Please see below video for example.
Also, not sure If I have mentioned this before but in the above video the first guy picks up the ball and throws it. You cannot throw the ball. You must punch it off your other hand as he does in the 2nd and 3rd examples. That is called a hand-pass and is the alternative to kicking the ball out of your hands or from the ground.