This is where either an admin or your kage gives you a piece of special paper.
You focus your chakra into it and has the following effects:-

Earth - paper crumbles away
Fire - paper turns to fire
Water - paper turns wet
Lightning - paper crunches
Wind - paper splits into 2

You can only learn jutsu of your element but as you go up in rank you can learn new element jutsu.

Genin - 1 element
Chuunin - 2 element
Jounin - 4 element
Kage/Sannin - 5 element
Ex-kage can use 5 elements as well