"Just starting out (again)"

#PokemonGO: About 2 years ago, I lost my account to some hackers. They deleted everything they could, transferred all my pokemon, my Dragonite and Tyranitar. Everything was gone. I contacted Pokemon and Niantic about it, nothing ever came from it. I deleted the app and moved on with my life.Now, I decided "why the hell not?" and downloaded it again. I missed the relaxation it brought and loved just being out. Since then, so much has changed, and I have forgotten basically all prior knowledge about the game. Can anyone help catch me up on basics/what's happened? I fell out about July 2017 and haven't played since. via /r/pokemongo http://bit.ly/2Wg37tO