@AC, who doesn't understand
The expansion of the universe is tough to grasp. The best explanation I have had is by analogy. Try to imagine a two dimensional man who lives in a two dimensional world on the surface of a balloon which is slowly being inflated.
As far as he's concerned, his entire (2 dimensional universe) is expanding. As he's only two dimensional, he has no concept of up or down, so there's no central point from which his universe expands; it just keeps getting bigger, seemingly from nowhere.
All the time this expansion is going on, he lives his life normally. In fact, his two dimensional glaxy attracts nearby two dimensional galaxies exactly as if the universe were not expanding (OK, it's a BIG balloon). They are still attracted to each other, even thought the balloon is getting bigger.
We're just the same, except that we're clearly three-or four dimensional aware, and the expansion is occurring at right angles to OUR reality.
Paris, because she's the one who explained this to me.