Question

"Endo” means ______.

Answer 1

Most usually "Inner", can also be a prefix for "Containing" aswell as "Absorbing"
examples.
Endocytos - Absorbing
Endoderm - Inner
Can't think of an example for containing but there are some.

Answer 2

Exactly as exuras has stated. Endo- is very much used today in different areas such as botany, zoology, anatomy...so on. And it means "in" or "inside". another ex.
Endonuclases: restriccion enzymes that cut the nucleotide chain in speficic places.
You will encounter many new words with this prefix as you go along learning biology. good luck!