Language skills includes everything from grammar & spelling to foreign languages.
Reading - top priority in homeschooling. You read to your child, they read to you, you listen to audio books together, you listen to other people reading. All of this teaches them to listen and spell and speak correctly. Vital life skills.
Writing - while less and less handwriting is being learned with the development of technology, it is imperative that we teach children how to write (both cursive and print) and give them the skills needed for life.