Meaning of the word "that is" in English

What does "that is" mean in English? Explore the meaning, pronunciation, and specific usage of this word with Lingoland.

that is

US /ðæt ɪz/
UK /ðæt ɪz/

Phrase

used to introduce a clarification or explanation

Example:
He is a polyglot, that is, he speaks many languages.
The meeting will be held next Tuesday, that is, on the 15th of May.