Conversations in channels can be seen and searched for by the entire team. You can participate in conversations, like or save important ones, mention specific people, so they see your message, and even edit a file that’s been added to the conversation.
When you go to any channel in Teams, the very first tab is Posts. Think of this as one big group chat. Everyone who has access to the channel can see the messages on the Posts tab.
The other important thing to know about messages in a channel is that replies to a channel message stay attached to the original message. This way, the whole thread of the conversation can be easily followed by anyone reading it.
To reply to an existing thread, select 
Reply, add your response, and press Enter
next to a message to show you liked it
to save a message for later
To start a new conversation to everyone in a channel, go to the compose box at the bottom of the Posts tab to start a new one. Next, type your message in the box and select Send 
or Enter. Now your message is in the channel.
Type "@" in front of a team member’s name while you're creating a message to include them in the conversation. The person will receive an @mention notice. You can @mention a team or channel if your admin enables it.
Look for the circle on the left next to Teams and Activity to see the number of times your name has been mentioned in a conversation.
Select Activity 
to see your Activity feed--a summary of everything that's happened in the team channels you follow.
1. Select the Filter 
icon
2. In the menu that pops up, select the type of notifications you want to see
3. Select X to close the filter
4. For a more specific feed, go to the Feed menu and select My activity. You'll see a list of everything you've been up to lately in Microsoft Teams
You know you have unread messages and unseen activity in a channel because its name appears bold. If you “favorite” the channel, it stays visible in your list.
You also receive notifications when someone @mentions you or replies to a conversation you're in, so that's another way you know a channel is active.
If you're worried about knowing whether a conversation is going on that needs your attention all your notifications appear in your Activity feed. You get a notification whenever someone:
If you want to adjust the notifications you're getting from a channel, here's how:
Go to the channel name and select More options 
> Channel notifications. This allows you to get notified of channel activity. You may also reset notifications to default.
Banner and feed will send notifications to your device and to Activity at the top left of the Teams app. Feed will skip sending notifications to your desktop and will only show up in your activity feed.
Want fewer notifications from a channel? You can turn them off from here as well.
Below are the different types of settings you'll find in channel notifications:
