1.) We can use function inside procedure but cannot use procedure inside function. 2.) Function always return value but procedure may or may not return value.

Main Diff is this one

1. Function is mainly used in the case where it must return a value. Where as a procedure may or may not return a value or may return more than one value using the OUT parameter.
 
2. Function can be called from SQL statements where as procedure can not be called from the sql statements 

3. Functions are normally used for computations where as procedures are normally used for executing business logic. 

4. You can have DML (insert,update, delete) statements in a function. But, you cannot call such a function in a SQL query.

5. Function returns 1 value only. Procedure can return multiple values (max 1024). 

6.Stored Procedure: supports deferred name resolution. Example while writing a stored procedure that uses table named tabl1 and tabl2 etc..but actually not exists in database is allowed only in during creation but runtime throws error Function wont support deferred name resolution. 

7.Stored procedure returns always integer value by default zero. where as function return type could be scalar or table or table values

8. Stored procedure is precompiled execution plan where as functions are not.
 
9.A procedure may modify an object where a function can only return a value The RETURN statement immediately completes the execution of a subprogram and returns control to the caller. 

A function always returns a value, while a procedure does not. When you call a function you must always assign its value to a variable.