i have to write factual description of a telephone. plsssss help me

You have not specified whether you want factual description of a telephone instrument or a mobile; or of a telephone's functions. Below is a description that includes all three; the following points can be elaborated:

-invented by Graham Bell

-helps connect people in all parts of the world

-important means of communication

-previously, only land lines available with big, heavy instruments

-these had a dial panel and a  receiver into which one could talk, along with an ear piece to hear what the other person was saying

-technological revolution and advancement has effected the field of tele-communication as well

-mobile phones have taken over the market, touch-screen models are the current rage

-instruments are many, advanced to include inter-net facility, e-mail, many other applications

-life is unimaginable without a telephone