capture skill

How are you supposed to capture skills? Can all classes do it or just 1?

Id really like help on this im pretty confused about capturing skills right now.

After you kill a boss, you can use it... see what skills he has, if you like one of them then take it, simple as that.

but is it a skill or something different that you use to capture the skills?

You use a Signet of Capture, which counts as a skill, to capture another skill for one of your two professions. You can obtain two Signets of Capture through two quests in Lion's Arch, or you can buy it from certain skill trainers later on.