Explanation:
Box 1: No
User1 coexistence mode is set to Org-wide settings, which is set to Skype for Business.
In this coexistence mode, users remain in Skype for Businessג €"not Teamsג€"for chat, meeting, and calling capabilities, and they don't use Teams for teams and channels.
Box 2: Yes
User2 coexistence mode is set to Skype for Business with Teams collaboration.
Use this mode to introduce Teams in your environment while you continue to use your existing investment in Skype for Business.
The "Download the Teams app in the background.." is on.
You can select the "Download the Teams app in the background for Skype for Business users" option. By default, this setting is set to On. With this setting enabled it will download the Teams app in the background for users running the Skype for Business app on Windows PCs. This happens if the Coexistence mode for the user is Teams Only, or if a pending upgrade notification is enabled in the Skype for Business app.
Box 3: No
User3 coexistence mode is set to Teams only.
A Teams Only user (also called an upgraded user) has access to all the capabilities in Teams.
They may retain the Skype for Business client to join meetings on Skype for Business that have been organized by non-upgraded users or external parties. An upgraded user can continue to communicate with other users in the organization who are still using Skype for Business by using the interoperability capabilities between Teams and Skype for Business (provided the Skype for Business users are not in Islands mode).
Reference:
https://docs.microsoft.com/en-us/microsoftteams/teams-and-skypeforbusiness-coexistence-and- interoperability