OS X has a built in VNC (Screen Sharing) server, but it is a little known feature that it also has a built in VNC client. No additional software is necessary.
To setup the server go to Preferences->Sharing and check the “On” checkbox next to “Screen Sharing”. Make sure to only allow access to Administrators or a specific user/user group.
You should see your computer name on the Screen Sharing configuration screen.
To connect to your computer from another one using VNC open Finder and press
⌘+k. In the Server Address enter
vnc:// followed by your computer name or IP address.
h/t Dillon Hafer