My guess also would be that this is the start of hand quilting.
You said that you are hoping to finish this quilt for Christmas. This year? Not sure how large the quilt is but if you are planning to have it done in less than 2 weeks and you have never quilted before, you may not finish it if you hand quilt. It really is time consuming.
If your goal is to give it to your mother on Christmas, you may be better off doing a simple stitch in the ditch by machine and then maybe adding some hand quilting inside the boxes after you give it to her.