255.0.0.0 is a larger host (computers, cRIO, Cameras, D-Link, etc) network which includes the hosts in 255.255.255.0. Competitions use 255.0.0.0 because they need more hosts. They run a flat network - all hosts are 10.x.x.x and with a 255.0.0.0 mask - they are all in the same network. All teams can technically communicate with each other and with FMS. This is why 255.255.255.0 still works, but your devices can only communicate with devices in 10.TE.AM network - just your team network - at least without a router.
You can use either one outside of the FMS system. It's easier to stick with 255.0.0.0 at all times.
IP Sub-netting is a great thing to know if you are interested in IT, Network Engineer, etc.
http://en.wikipedia.org/wiki/Subnetwork . I'm a little rusty at it. There are many iPhone/Android apps for IP sub-netting.