I enjoy using Facebook Messenger. (Although, I try to avoid FB itself.) See my thoughts from a couple of weeks ago for details. As I said before it is a very useful tool for communicating. Keep in mind that for Messenger to work both you and the person you are communicating with have to have Facebook accounts. You both also need the Facebook Messenger app on your phones. You may also use it on your Facebook site on your PC without installing anything as it is a built-in feature.
Let us say that you and several other friends are planning a trip and want to discuss all of your plans and options. An easy way to do so is to start a group chat in Messenger. Start up a regular Messenger chat the way you normally do. Add a person at the top by typing their name in the search area, when they appear in the list tap to add them.
Now all you do to start a group chat (defined as three or more people in a chat session) is search and add whoever else you would like to join. According to Facebook’s information, you can either add a maximum of 150 people in one chat or it is unlimited. I found both answers while researching and I have never had more than six or seven. I also cannot imagine having 20 people in a conversation much less 20,000 but maybe someone can.
Once you start a group chat that chat will remain in case you would like to continue it at a later date. You can also name the chat. My wife has one with her three sisters and herself in it, named “Sisters.”
You can also remove people and add new ones to the group. If you created it you have all the power. I will not get into how you can perform all of the many functions in a group. However, I will give you this link (rd.dblclx.com/fbg) to the FAQ page for FB Groups.
You may be added to a group without your consent until you receive the chat. A friend may add you to a group session and send messages seven days a week, 365 days a year. You will receive the conversation as well as everyone else in the group. This is good if you are setting up a meeting. However, if they are in a different time zone you could get messaged multiple times at 2:00 a.m.
You can stop it without their knowledge. On your Android device navigate to the conversation you want to leave. Press and hold your finger on the conversation, select “More” from the list. Choose “Do Not Disturb” which does not notify the group you are ignoring them. You will be able to follow the conversation later. You will be informed you will no longer get conversations from this conversation and it will be removed from your device.
You may also select “Leave group” which will remove you from the group. It will also notify the group that you left. iPhones may vary. If you have a problem finding these choices, go to Facebook on your computer. The controls are easier to find with the Options button (looks like a gear).