Exactly what is être?
I know it means "to be" but I'm having difficulty understanding what exactly that means under certain context.
This verb (être) has so many senses in French. Perhaps this other link.
I am a big fan of dictionaries, if this link is too difficult for you, try to look for another online dictionary, there are so many beautiful explanations about spelling and grammar. Because your question, which seems simple, covers an lexical scope that is very very vast.
So perceptive my friend. ☺
But it is true - I am committed to trying to do this now. I'm far from fluent but I have learnt a lot and questions I can't answer make me research the grammar - usually through the WordRef forums - which are a terrific resource to get answers from native French speakers like your good self. ☺