Announcements are useful for posting things you want all the students in your class to have access to. For example, I would use announcements when I wanted to hand out note sheets for the students to fill in this. This was quick, and there wasn't an assignment attached to it. The other benefit to this I found is that students that used Google Classroom on their devices and signed in with their school accounts would get a notification if you posted an announcement. This made sure they all ready them. To create an announcement in Google Classroom, follow these steps.
1. Navigate to the class you would like to post an announcement.
2. Once there, click on the plus button in the lower right corner of the screen.
3. From there choose "Create Announcement." The following box pops up.
4. Write what the announcement is in the blank, attach any documents you would like, and then click post.