/diy/ - Do It Yourself

Got a hole on my roof, just found it yesterday after removing a giant branch that fell on my roof last week. Looks like it went down to the wood. I watched youtube videos about replace shingles which seem to make sense.

I didn't see anything about replacing the felt material that is under the shingles. Do all roofs have felt under shingles? What do I get to patch the felt thing under the shingle?