Each member of the team has a different set of abilities particular to his or her character. For example, the Marine has an inflatable raft, scuba gear, and a harpoon. The Spy can wear different uniforms he finds in certain levels and distract enemy guards. The Green Beret can climb certain walls and carries a noise-maker decoy. One of the special characters, a female spy, can distract multiple guards by dancing.
Some abilities are the same, or have the same effect across commandos.
For example, a couple of the commandos can knock out an enemy with a punch, and the spy can have the same effect with a chloroform-laden cloth. Forming your opposition are the guards. There are a couple of different types of guards, the only major difference between them being that the Gestapo cannot be fooled by your spy. Some guards are stationary, surveying an area from a fixed position, while some run routine patrols. You can shift-click on a guard to see his field of vision, represented by a green cone emanating from the guard.