Within Microsoft Teams you are still able to maintain a list of 'Favourite' or otherwise grouped contacts. Here you will be able to view colleague presence and initiate 1-to-1 chats just as you would have in Skype for Business/Lync.
To view your contacts, click the "Chat" app from the left hand side, then choose "Contacts" from the top:
Click "Create a new contact group" at the bottom to add your own named group.
To add a contact to a group, click the three dots to the right of the group name and select "Add a contact to this group". Search by first or last name, click the contact and then click the "Add" button.
Once added to a group you can click on a contact to start chatting. Users can also use Teams to video/audio conference and screen share using the buttons to the right:
Please note, all chat history within Teams is permanent and cannot be deleted by users.