Meaning of the word "by heart" in English

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

by heart

US /baɪ hɑːrt/
UK /baɪ hɑːt/

Idiom

learned or memorized completely

Example:
She knows all the lines of the play by heart.
I learned the poem by heart for the recitation contest.