The rogue hiding in the shadows, the steely eyed martial artist, these are examples of strikers. In game terms a striker is a character that can do a lot of damage but can’t wear much armor, making their defenses relatively low. usually a striker has special abilities that helps increase their damage in special ways (for example a rouge will be able to find weak points in the enemy’s armor or a monk or martial artist can deliver a series of rapid punches and kicks.) The striker can be a very fun an fast paced character to play.
Playing a striker is a balance between dealing as much damage as you can, and getting out of the way of any counter attack. Strikers can take some damage though not as much as a defender class, so avoiding damage is a necessity. This can be done by keeping your distance from the enemy and using a ranged weapon like a bow or sling. Getting away from the attack is also a good way. Some striker classes have movements attached to their attacks, gaining some distance from a threat.
Players need to keep the balance between damage and avoidance to play well.