Sentences can be in the first, second or third person.
I like playing tennis. (first person)
You like playing tennis. (second person)
She likes playing tennis. (third person)
We can also classify sentences as singular or plural.
If we are talking about one person or thing, then the sentence is singular.
I like swimming. (first person singular)
If we are talking about more than one person or thing, then the sentence is plural.
They like swimming. (third person plural)
Sentences in the second person are the same whether they are singular or plural.
If somebody says, 'You must come home now,' they might be talking to one person or to more than one person.