You are in a room, the band up at one end, the caller shouts:
You know Longways. You have asked someone to dance, you have walked up onto the dance floor and joined one the sets that are gradually forming.
Quite often the caller then reminds you with a:
which is a shorthand for sorting yourselves out. In this case into small circles of four people, the top two couples, the next two couples, the next two and so on down the set.
But then comes:
Which is saying, if you've got your little circles of four sorted out and know who the 'first couple' and the 'second couple' are (the 'first couple' is the couple closer to the band), then the two people of the first couple should swap places.
As always, it pays to remember that people of either sex may be dancing the "men's" role and similarly for the "women's" role.
So, previously if you looked along the set, you'd see a line of "men" facing a line of "women". After the first couples swap places you see a line with "man", "woman", "man, "woman"... facing a line with "woman", "man", "woman", "man"...