Microsoft introduced the Chat Bubble feature in Teams in July 2021. This means that chats sent during a Teams meeting will appear on the screens of all meeting participants. This can make it a little easier to see the chat messages during a meeting. But, if the chat is active then it might make it less helpful. This really depends on the activity: if there are lots of messages coming to the chat all the time it will not be fun to get flooded.
Chat Bubbles are enabled by default. If you wish to disable them in a meeting, use the “More” button (the three dots) in the Teams meeting action bar and select the Don’t Show Chat Bubbles item in that menu.