The quickest for teachers using Google Classroom is the "question" post option. You can have students respond to a question you post, as well as to each other's responses. You can even allow students to post messages to the classroom stream, and use those as discussion questions. This is a quick and easy way to get and keep the class talking even after the class is over.
Another option through G Suite is a Google Hangout. Using your class group, you can set up a Google Hangout that students can join as an online project group, study session or informal support. It can be a scheduled event or always open. With you as a member of the group, you'll know what the group is discussing and can participate as needed. Here's how to get started with a Hangout.
Padlet is another online tool, similar to a virtual Post-It wall, that allows students to post and respond to questions, and which allows a digital archive of interactions.
Interactive discussions allow for a great range of participation from voices who may not always be heard. They also empower students to seek their own answers, while "slowing" the conversation to allow teacher intervention where needed.
