What does "in one's element" mean?

In a situation which is entirely suitable, familiar, or enjoyable.

In one's element

prep_phrase

prep_phrase ·Rare ·Advanced level

Prep_phrase

1
In a situation which is entirely suitable, familiar, or enjoyable.
"You can tell he's completely in his element when he's talking about fossils."

"You can tell he's completely in his element when he's talking about fossils."