Help with snow functions in my car?

So it's snowing today and the snow plows haven't gone down my street yet. I am a teenage driver and have some experience but I haven't driven through snow before. On my car (automatic not mannual) below the drive gear theres a 2 gear and a L gear? Also on the side of my gear shift theres this thing that says D3 (is that like third gear or something)? Apparently it's supposed to help with snow? Also theres a on at the base of the gear shift labeled snow so I'm uming I should push that. If I use any of these features do I have to be aware of either not exceeding a certain speed or any other precautions? Thanks in advance I'm 17 and haven't driven through snowy conditions.