Good question! I've noticed a fair amount of confusion on the forums as to what OSC is. Many people confuse apps that use OSC with the protocol itself.
So what is OSC?
OSC (Open Sound Control) is a protocol for communication between devices. It's a specification which allows devices to talk to one another in a standardised way. That said there is a great deal of flexibility in the protocol.
TouchOSC is not OSC!
So what is TouchOSC? TouchOSC is an app which uses the OSC protocol to send OSC messages. These messages can be formatted to talk to a wide range of OSC compatible devices. This makes TouchOSC ideal to create your own remote for Eos or any other device. oscRFR is another great example but this is directly aimed at Eos control.
What else can OSC be used for?
OSC can be used for many other purposes. Triggering and synchronisation (think MIDI Show Control). Mapping sound information to lighting/video parameters. Handing patch and show information between documentation software and a device. The list is endless.
Hopefully this will be a help to some users!