procedure :- perform an action

Function: - Function used to compute a value and return a value

1) stored procedures are designed to return its output to the application.
A UDF (User Defines Functions) returns table variables while a SPROC can't return a table variable although it can create a

table.

2) UDFs can't change the server environment or your operating system environment
while a SPROC can.

3) when T-SQL encounters an error the function stops
while T-SQL will ignore an error in a SPROC and proceed to the next statement in your code
(provided you've included error handling support).

4) a SPROC can be used in an XML FOR clause
a UDF cannot be.

5) If you have an operation such as a query with a FROM clause that requires a rowset be drawn from a table or set of

tables then a function will be your appropriate choice.
However when you want to use that same rowset in your application the better choice would be a stored procedure.

procedure: It may or may not return a value.

function: It always return a value.

procedure :it can't be used in select query.for example if we have a procedure abc(salary number ) then we can't use it as select abc(salary) from employee.

whereas we can use functions in a query . select sum(salary) from employee