In SQL, is it composite or compound keys?
Both composite key and compound key describe a candidate key with more than one attribute. According to the Relational Database Dictionary (C.J.Date) they mean the same thing.

In ER modelling the term "compound key" also has a more specific meaning. It means a key whose constituent attributes are references to keys in other entities - i.e. a compound key forms an identifying relationship. For most purposes, this isn't an especially useful or important concept so the terms composite/compound are often treated as interchangeable. It's probably best to stick to "composite key" unless you are referring specifically to the ER modelling concept of a compound key.