Pages in Personal or a team now have the team in their address, such as /t/acme/notes. Each browser tab keeps the team in its address: switching in one tab no longer changes your other tabs, and Back, reload, bookmarks and copied links open the page in the team they were made in.
An address without a team, such as an older bookmark, opens in the team you used most recently. A link to an item from another of your teams, such as a link in an email, opens in that item's team instead of showing that the item was not found. Search and Recent work open results from another team in that team.