Google Classroom is relatively new to the G Suite in education. Classroom allows teachers to create a class, add students, and directly assign and receive student work from his/her students. All assignments are automatically organized in the teacher's Google Drive under a folder titled "Classroom." There are three tabs total in each Class: Stream, Students, and About.
Stream: Assignments, Announcements, and Questions can be posted to students and they will appear in the stream by date (much like Facebook, new posts are on top). New posts can be created by clicking the "+" button in the bottom right-hand corner. If a teacher creates an assignment and attaches a Google Drive document to the assignment, he/she can choose to have Classroom make a copy for each student in the class (rather than having to deal with sharing settings).
Students: Teachers can directly add students from the Contacts or handout a unique class code that students can use to join the class themselves. As students join, they will be listed in this section alphabetically. Teachers can also choose to send guardians updates through the Student Tab as well.
About: A very simple descriptive page with specifics about the class. Many teachers attach the class website URL here so students can go between the two easily.
Google Help Center: Classroom