Controllers (at least in Canada) have 2 ways of communicating with other controllers (other then just shouting down the line), which are hotlines and interphones.
Interphones work exactly like your home phone would, except you don't dial a number, you just hit the button on the touch screen for who you want to call (although if something breaks, there are numbers assinged that you can dial the old way). The phone rings, the other controller answers, and the line stays open until someone hits end. The interphones are typically used for longer calls that aren't as time-critical, for example passing estimates. There are also interphones to all the non-control positions such as Flight Service stations, Flight planning, etc.
The hotlines are used for more time-critical matters, or for very short items that don't warrent a call on the interphone. Hotlines are operated using the same touch screen as the interphones, but the big difference is when you touch the button for the hotline to another controller, you are instantly talking to him. As long as your finger is on the button, everything you say is going right into his ear. The hotlines are used for things like handoffs to other centers, coordination with other controlllers (i.e. could you send ABC123 direct XYZ for traffic, etc.), and pretty much anything else other then passing estimates.