We use this (singular) and these (plural) as pronouns:
- to talk about people or things near us:
This is a nice cup of tea.
Whose shoes are these?
- to introduce people:
This is Janet.
These are my friends, John and Michael.
WARNING:
We don’t say These are John and Michael.
We say This is John and this is Michael.
- to introduce ourselves to begin a conversation on the phone:
Hello, this is David, Can I speak to Sally?
