What are the various branches of scout?

In the US (other countries have different systems)

For grade school age boys there are the Cub Scouts which actually are divided into three divisions:

Tiger Cubs - 1st grade

Cub Scouts - 2nd and third grade (Wolf and Bear Rank respectively)

Webelos - 4th grade to mid- 5th grade.

For 11-18 year old boys there is the Boy Scouts.

There are also Sea Scouts and a Venture Scouting program which is co-ed and for 14-21 year olds.