Explanation of Birth Control Patch?

I have been using the patch for about 1.5 years (Xulane). I love it because of the way I apply it and the minimal side effects (I only get headaches and sometimes a lightly aching back). I use it exactly as stated and have only missed one or two patch change days (caught it the next day and changed!). However, my doctor never explained to me exactly how the patch works. Would someone be willing to explain?

I have googled and am still a little confused about what I’m reading. I just want to know what’s going on with my body so I can continue to treat it right!

My boyfriend and I also use condoms as extra help but recently have been going raw w/ pull out, and he wipes off his precum. Just wanna make sure I am doing everything I can to prevent pregnancy. I’m not in the mood for a baby right now!