so I lost all my photos on my Samsung Galaxy S3, I tried photo recovery sites and was asked to root my phone what does that me

You should not need to root your phone for that, I have used a piece of software called PhotoRec both on my Android phone and the SD card in it. It works on pretty much anything and I got my deleted pictures recovered. My phone isn't rooted so yeah. You can find a tutorial on how to use it on their website, it's pretty easy.