Connections is described as 'allows you to connect to and use other desktops. This can be a great way to access content or software on a different desktop operating system. It can also be used as a way to provide support to users who might need help' and is an app in the Network & Admin category. There are more than 100 alternatives to Connections for a variety of platforms, including Windows, Mac, Linux, Android and iPhone. The best alternative is TeamViewer. It's not free, so if you're looking for a free alternative, you could try Chrome Remote Desktop or Remmina. Other great apps like Connections are AnyDesk (Free Personal), DWService (Free, Open Source), mRemoteNG (Free, Open Source) and UltraVNC (Free, Open Source).
Remmina is a remote desktop client written in GTK+. Remmina primarily targets system administrators and travelers that need to work with computers remotely in front of either large monitors or tiny netbooks.
DWService is an open source project which offers a service that allows access to remote systems (Windows, Mac, Linux, Raspberry...) using a standard web browser - without any component required on the client side.
UltraVNC is easy to use and free software that can display the screen of another computer (via the Internet or a local network) on your own screen. The program allows you to use your mouse and keyboard to control the other computer remotely.
TightVNC is a free remote control software package. With TightVNC, you can see the desktop of a remote machine and control it with your local mouse and keyboard, just like you would do it sitting in the front of that computer.
X2Go is an open source remote desktop software for Linux that uses the NX technology protocol. X2Go can be used to access PC desktops, but its main use case is providing secure standalone remote sessions via ssh.