Question

write the difference between number and autonumber data type

Answer 1

Number type can store any integer/float value, depending on decimal precision specified. Whereas Auto Number will have values calculated by system.(Auto Incremented Values). You don't have a control over those to change them.

Answer 2

A data type which can be used to automatically store monetary values with.

Autonumber data type will automatically increment whenever a new record is inserted.