Medicaid and bills

Not sure where to post this. I have Medicaid now I got approved 3-4 weeks ago. They take bills back from February. So today going through my mail I got my recent doctor bills that are from February-march. I went in a week or two ago I believe to give them my Medicaid information(I switched doctors/offices for my last appointment and just got around to stopping in that office) so I'm confused why I got those medical bills. Do they just always send them to me as well for record or what? I'm sure I just need to call and ask I just didn't know why I get the bills sent to me. And how do I know what Medicaid takes care of like if they pay for it 100% or if I'll have to pay some of it to.