the void. emptiness. these have nothing to do with what they sound like.
emptiness isn't any "thing" that has space where there once wasn't any. or space where there could be something. if you want to think of it in definite ideas, it is simultaneously completely full, completely empty and every degree of empty and full at all times.
additionally, there is no vessel. there is nothing to be empty, or void. similarly, it is not a space filled with nothing. or nothing surrounded by nothing.
the void is everything, realized in a way unique to traditional thought. it is 100% everything. 100% reality as you know it, including yourself.
then why do we call it emptiness? because while there is no such thing as time as most people understand, the mind lives in a reality where time is thought to be a thing, so in order to appeal to the unrealized mind, we use words. words reflect an idea that we can both relate to. we can never know that "emptiness" means the same thing for us, in terms of a glass being half full or half empty, as the idiom goes. of course, we have a pretty damn good idea we have a similar idea if we're both looking at the same glass at the same time. there we can relate. and through words we relate to each other as best words can do to relate an idea.
but what if you can't see or hear or taste or touch of smell this thing. if you were trying to explain an idea that had none of these properties (or all of them, indistinguishably from each other) then how would you describe it to another?
this is zen.
any words, but especially words such as "void" and "emptiness" aren't an ideal choice of communication, but they are all we have, and as such are adequate. adequate presuming the listener is given a fair advanced warning that they must attempt to unlearn the idea that these words have a fixed meaning. understanding that a word is nothing but an abstraction. a tool. a word is a symbol for an idea. neither of these things are at any time fixed in space or time. and as such can mean anything so long as we think they do.