Online classroom discussions come in a few different formats. 
“Real time” chats are good for discussions with a set time. For example, if you are showing a 4-minute video clip and want students to brainstorm questions they have about the science behind the topic, a “real-time” chat would be good for brainstorming. These are called “synchronous” chats. Another example would be having a “back channel” discussion while you are teaching a lesson. Students can post comments and questions about the material you are presenting. You often see this happen naturally at large conferences where there are hundreds of people watching a keynote and discussing some concepts using social media. 
“Asynchronous” discussions are good for when you want students to think about, formulate and share a more formal response. Perhaps a debate. Perhaps sharing research about a variety of topics or situations. These discussions happen over time, not all at once. 
Below are some suggestions on tools that can be used for each type of discussion.

“Real time” chats

Real-time discussions online are great to use during work periods, for sharing resources, to pose questions about videos, to discuss topics during lessons or videos, etc. 

Tools for real-time chats:

Todays Meet


“Asynchronous” discussions 
Asynchronous discussions are great for conversations that carry over the immediate period of learning. They are great for reflecting, sharing work, sharing resources, collaborative problem solving and responding to prompts. 
Tools for asynchronous discussions: