Google Docs is a free online word processing application. Students are able to compose writing pieces using Google docs and it automatically saves to their Google drive so no chance of losing it or "the dog eating it". Google doc is fully integrated into Google Classroom for ease of submitting assignments. Teachers can view version history of documents and turn on suggestion mode for either peer or teacher review.
Grammarly is a revision app that aids students in making corrections to their composed writing assignments. The free version works like spell check, finding and giving suggested spellings to misspelled words in the text. What I love is that the free version also tells my students what advanced grammar problems that are found in the paid version but it doesn't show them where. Students know the problems they are looking for and must find and correct them on their own. Because Grammarly scores their writing, students find it fun to find and correct mistakes to raise their score. It almost makes a game out of revising papers! Grammarly intergrates with Google Docs so students can make corrections in one application.