A pair of is how English counts things that come in twos. Shoes, gloves, socks.
The odd part is that it also counts single objects made of two joined halves, so a pair of trousers, a pair of scissors and a pair of glasses are each one thing. That construction has no logic left in it and simply has to be learned. It also counts people working together, so a pair of detectives, and animals, so a pair of swans, which mate for life.
1phrasepair ofUsed before a noun to indicate two matching items or one two-part object.
“He bought a pair of boots in the sale.”