>>Would the small file also have worked?
Note that the small file ends with .SHA-256. This file is the HA-256 checksum for the ZIP file download. You can use the checksum to verify that the ZIP file downloaded correctly. Ditto for the second link ending in MD5.
The items with 'src' in their names are source code.
The items with 'jdk6' in their names are specifically for use with JDK 6, the ZIP file without 'jdk6' is for use with JDK 5.