I am using Ubuntu 12.04 .while looking around terminal and i came across two things . one is xterm and xterm(Unicode) , may i know what the difference between these two things ?
The question posted by maythux provides some valuable alternatives to either of the terminal emulators you mentioned.
Like devav2, I assume you are talking about uxterm when you mention xterm(unicode).
xterm is a very old terminal emulator for the X server system. In fact it is the original X terminal emulator from the 1980's. Unicode is a method of encoding into digital form all of the symbols used by people to communicate when they use their native languages.
Programs that have been fully internationalized, meaning fully able to process any language, will output in unicode rather than ASCII. Even if you are using ASCII or Latin as your native script unicode will work since they encode the same. Other systems of symbols may not be compatible.
Still more systems of symbols will only work with unicode.
Because it is taking a while for programs on every platform to be converted to use unicode some programs do not output it. If you are using such program and unicode is giving you a problem with uxterm, straight xterm may work better.
The gnome-terminal program many use also supports the output of unicode, but that can be changed by changing an option.
For more information on unicode you may find this wikipedia page useful.