How to change a light switch?

2 Gang means two separate switches mounted on the same plate - for switching two separate lights.

2 Way means controlling one light from two separate sattions such as a landing light that may be switched from upstairs or downstairs.

Terminal means the hole with a screw into which you put the wire(s)

Old light switches often have just two teminals and from what you say one of the terminals in one of the switches had two red wires going into it - Put these in the Com or common terminal hole. Put the associated black wire into either L1 or L2 it doesn't matter which but remember it will be live when the switch is on.

For the other switch place the Red wire in Com and the Black wire in L1 or L2 as you wish.

You may wish to consult these two links...
Operating one lamp from two places (two way switch)

http://www.electronics-project-design.com/images/TwoWayLightSwitch.GIF

All about switches
http://en.wikipedia.org/wiki/Switch

Take care...Good luck...

Peccavi
April 2009