Recent Builds are experimental builds released by coders in order to test new features or bugfixes. They may offer enhanced graphics or gameplay, but are not as thoroughly tested as official builds. They may cause pilot file corruption (causing you to lose all campaign progress) and it is strongly recommended that you backup your FreeSpace 2 pilot files before using them. Other serious bugs may appear when using them.
If you are trying to install FS2_Open for the first time, use the automated installer.
Only veteran users should use recent builds.