Insert but Don't Commit MySql

I am pretty new to MySql and Databases, and I was wondering in python sometimes I forgot to commit after an insert, and then when I do then next insert and commit that one the, auto-incrementing id column has skipped a number. So I was wondering what happens when you insert and forget to commit is this bad for the Database? Or does is just skip because when you insert it assigned an id to it but didn't save it? Thanks