@ anvesh do read this guide to know more about ubuntu
www.ubuntuguide.org
ANd you can find many useful books on linux for reading at
TLDP for free. They are very useful in understanding linux.
All the 3 distros you got are good and easy to use, it just depends on personal preference and sometime it can happen that some hardware of yours might work fine in one but not on others so that's your choice on which one you'd like to use.
@saurabh.sauron You don't go on converting every singe file you find to .deb for installation. It is not considered as a good practise. The best way to install any software is from source and you're recommending to convert a source file to deb? And you should first check if there's a file available for your distro before using a rpm. Alien command will convert the file into deb but still it won't satisfy the needs of youtr system. Every system has a slightly different configuration and organisations. That is why even a deb for debian isn't recommended for use with ubuntu or a rpm of fedora for suse and so on.
Try to get the software optimised for your distro. But the best way is to compile from the source.