Electives are courses that you can "elect" to take purely out of interest--because they are not something that you need in order to fulfill a major, general education, or minor requirement. Almost every student needs electives! The exact number you need is a question of math. If you need 120 semester hours minimum to graduate from UNC Charlotte... let's say you need to spend about 45 semester hours on general education requirements, and 48 semester hours on major and minor requirements. You've got 27 semester hours left over to fill with... what? Some students will decide to add a second major, thus "spending" these 27 hours, which otherwise would have been electives, on a second set of major requirements. Others will add a minor or certificate program, and then fill the remaining needed credits with their elective choices.
Anecdotally, it often happens that students start off at UNC Charlotte being very focused on completing the general education requirements. This is good, obviously. But if all you ever take in the Freshman and Sophomore years are general education courses, guess what? In the Junior and Senior years, you will have run out of major/minor/general education requirements to fulfill, and will actually be forced to take many courses purely as electives--and for some programs (e.g., Business), a certain number of these actually MUST be outside of your major. It seems to most advisors that a smarter plan is to take one to two electives each semester--this has the advantage of allowing you to take some major courses in your Senior year (at which point you'll have first choice of these courses, and can hopefully really enjoy your selections), and also gives you a chance to explore possible minors/second majors/areas of interest along the way.