What is difference between stored procedure transformation and external procedure transformation?

In case of storedprocedure transformation procedure will be compiled and executed in a relational data source.U need data base connection to import the stored procedure
in to u’r maping.Where as in external procedure transformation procedure or function will be executed out side of data source.Ie u need to make it as a DLL to access in u r
maping.No need to have data base connection in case of external procedure transformation.