1.  Function must returned a value,but stored procedure is 
not necessorly returned value

2. A function can be used to calculations,but sp used to 
solve a business logic

stored procedure when executed generates execution plan 
once and next time when it is executed again it will use 
the generated execution plan,it does not generate it again.

Function compiles from the beginning and prepares the trace 
or execution each time it is called.

stored procedure is precompiled one but Function not( want
to compile each time)

1-Function can not return the value but store procedure 
return value
2-Store procedure is pree-compile statement but function is 
not pree-compile satement.
3 function fallowed by select statement but store procedure 
fallowed select, insert,update statement.