The more fundamental the concept, the more difficult it is to explain. That’s what they say. I have a hunch that it might be true, too. What is a “feeling”, for example?
What was time to you? Wikipedia wasn’t that bad in explaining the concept in physics-terms, I think.
Then, what is “space” to you?
Wikipedia says this:
That’s ok in a way, even though events having an extent and a direction seems a little weird.
[The meaning of space,] whether it is itself an entity, a relationship between entities, or part of a conceptual framework [is still discussed on a fundamental level].