What is difference between Oracle API and Oracle SQL Loader?

"Oracle SQL Loader" is a direct upload utility available in Oracle DB , using it you can get data from a text file directly into a database table in oracle.

"Oracle API" is a set of packages prepared by Applications teams to give the programmers a facility to design and create their own upload process.

Usually we use the SQL Loader to get the data to a temp table in the DB then we use the APIs to apply the rules we need and to upload the data into Oracle eBusiness Suite.