When you have completed your track in your DAW you will need to export it to a single audio file to upload or distribute. There are two main formats to choose from which are WAV and MP3 and I will explain what ones to use and why.
The first thing to decide is what you will be using the exported audio for for. The purpose of the file will determine what format is required.
WAV - WAV is a non compressed format with the highest audio quality. You should use WAV format for CD, DVD, iTunes, Google Play, TV or any other media requiring the best audio quality.
MP3 - MP3 is a compressed format with the varying audio quality. They load quickly and the file size is small and they play with a reasonable sound quality. The level of compression will determine the overall sound quality but usually for online streaming MP3 is the best choice.
Now you know the difference between the two I will tell you that I prefer to use WAV almost all the time when saving and audio file then I will create an MP3 file of tracks I intend to have streamed online.