Classroom is the online learning tool provided by Google. Its most important advantage is the full integration in the Google environment which include access to google docs, sheets, slides, drive, meet and calendar. Thanks to Google Classrom teachers can, upload documents, start collaborative work, give assignments to students and grade them, and comment on their work. You can also collaborate with the whole class simultaneously on a dedicated google meet. Its very simple and ready to use layout is another strenght of Classroom, bacause teachers can set-up courses in few minutes.
Google Classroom presentation: https://www.youtube.com/watch?v=DeOVe2YV2Io