I need help with my AVI file

I have a video camera but it only records in AVI format - i have no idea what any of the technical things are i just want to be able to play the files on my macbook air which its not letting me do - these videos i want to put on iMovie to make a video what do i need to do to do this - i didn't really want to download anything but i suppose if i had to i would have to so if any one can help i will be grateful!! THANKS 🙂