What are halides? What are some examples of them?

Halides are anions of the Group 17 elements, the halogens.
The halogen elements are diatomic molecules, ##X_2##, that can be easily reduced:
##X_2 + 2e^(-) rarr 2X^-##
The anions are the so-called halides: ##F^-, Cl^-, Br^-, etc.##
Of course, if you have a negatively charged species, there must be a positively charged species as well to balance the charge, typically a metal cation, ##Na^+##, ##Mg^(2+)## etc. The best known halide is the stuff you put on your fish and chips :
Of course, I could broaden my horizons a little bit, and consider organic halides. A halogen atom can be tacked on to an alkyl or hydrocarbyl group to give an organic halide, where the halide takes the place of a hydrogen. With hydrocarbons, this is usually the first step of a synthesis, because once the halogen group is introduced (##Cl## or ##Br##), you can start doing selective chemistry on the organic chain.