The first one is for converting any file format. If you are on a computer that doesn't have a certain program you could use this site to convert the file to other formats. Convert file formats online.
The second one is for creating thumbnails for photos quickly on the web when you have no photo editing software. quick thumb nail.
The third one is for converting any file into mobile video format. This is so useful when you only have mobile in your hand and want to watch something on the web, Convert any video into mobile video format.