Use the word "pair" for two things that match or are part of a set, especially clothing:
I need a pair of socks to wear.
Bob bought a pair of pants. (It’s a pair because the clothing covers two legs.)
Sheila needs to get a new pair of glasses.
Get yourself a good pair of hiking boots if you walk long distances outdoors.
a pair of hiking boots
The word pair is also used for people, animals, and things that go well together:
Theresa and Ned make a nice pair.
A pair of cardinals are making a nest just outside of our window.
The teenagers at the dance paired off as the evening wore on. (The word "pair" is used as a verb in this sentence.)
Do you know how to pair wine with food? (Connoisseurs of food and wine often use "pair" as a verb.)
The word "pair" is technically a singular count noun; however, many speakers of English regard it as plural. I think it depends on where the word appears in the sentence.
There’s a pair of skates in the box. (singular verb)
There are several pairs of skates in the box. (plural verb)
A pair of sunglasses at that store sells for over $100! (singular verb)
A pair of sunglasses sell for over $100. (plural verb)
Note: Americans who pay close attention to grammar will usually consider the word "pair" singular and make the plural form by adding an "s." In British English, the word "pair" might be regarded as a plural noun (But I’m not sure.)