Thre are mainly three types of functions in SQl server 2005.
1.) Scalar function
2.) Inline table valued function
3.) Multi statement table valued function

Three types

1) Scalar
A scalar user defined  function returns one of the scalar
data type .text,ntext,etc

2) inline table Value
An inline table value function return a table data type

3) multi -statement table value function

A multi -statement table value function return a table and
is also an exceptional alternative to a view as the function
can support multiple t-sql statements to build the final result