Bug spray
Bug spray is a chemical in a spray can that is used for killing bugs or keeping them away.
Bug killer
Some bug sprays are sprayed at the bug to kill it. Other bug sprays are sprayed around a house or picnic area. Bugs that come too close to this kind of bug spray will usually die.
Bug repellent
Bug repellent is never sprayed at a bug. Bug repellents can be used to keep bugs from coming into a house or picnic area. Some kinds of sunscreen have bug repellent that keeps mosquitos away. Some bug repellents are spread over the skin of a person.