Let's try this:
Take a large sheet of elastic material. It can stretch indefinitely.
It starts off 1 yard on each side. And then is pulled on so it stretches evenly in all directions at 1 foot every 10 seconds.
Now let's put a whole bunch of ants on it. If they stand still they get farther and farther apart. If Ant Abe is on one side of the sheet and Ant Babe is on the other they are getting 2 feet further apart every 10 seconds. That is probably faster than an Ant can walk, eh?
But Ant Tom and Ant Bob are near each other on the sheet. They are not getting farther apart very fast at all. Perhaps very slowly. If they are only 6 inches apart they are 'receding' from each other at only about 4 inches in 10 seconds.
The motion of the ants because of the stretching of the sheet if like the galaxies being moved farther apart by the expansion of space. The galaxies and they ants are NOT moving at all. They are staying at the same place on the sheet or the same place in space. However, the places they are "staying" are being moved farther apart.
Now let's have the ants move around on the sheet. This is like the galaxies actually moving around in space. Now if two ants aren't too far apart they could move toward each other and collide. Likewise two galaxies could happen to collide if they were not too far apart.
As noted elsewhere a few million light years is "close" just like inches on our elastic sheet.
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