Aspect means a part or feature of something. If you are going to vote for a candidate, you should first learn about the various aspects of her political agenda.
At the heart of the word aspect is the Latin specere "look" (think spectacles). Later, the word became connected to the idea of what can be seen from a particular position. Whether that means you can see all of something (all aspects) or only part (one aspect) depends on where you are standing and how hard you are looking.