2019 didn't file 2018

I'm trying to see how this is going to work out if you will. I didn't file in 2018. I notice while filing 2019 at some point I was ask did I file 2018? I stated no so that I could go ahead get penalized or whatever. I paid taxes throughout the year each pay so I would not have to pay at the end of the year. however, I got a little more after ready to efile. I'm wondering if IRS included 2018 with my 2019. I don't know how this works and hope it can be explained. I was accepted on the 8th and IRS has received my taxes being processed.