Advance features of a rar file ext

Usually in the office i would be asked to zip some files and email it to clients, there are times when i would just immediately click on stuff not knowing that those words mean and what difference it does have. I have been using a zip format for packing files into one data but from the software, there are two options though, one would be the .zip and the other one is the rar file ext or extension. I might wonder if what would be the features of a rar file ext as i believe this one is the latest of the two?
