Using Teamviewer or something similar would be the easiest way and not need a VPN.  Google Chrome has a remote desktop plugin too.  Both Teamviewer and the Chrome Remote Desktop can be setup for unattended remote access.  A word of caution, Teamviewer has been cracking down on license abuse.

A VPN is Virtual Private Network.  It essentially extends your local network over a WAN (public) connection to a remote device or network (office to office).  They are also used to provide secure routes to the internet and prevent malicious activity when connected to a public network.  If you are not familiar with how to use the likes of Teamviewer, a VPN will be overly difficult to configure and use.  Its not necessary in this instance either.