Wide Area Network (WAN) is a network connection method for remote (or traveling) users, or branch office to  central site/headoffice network.
Typical Users and An Example of WAN Scenario:

Mobile Workers/ Business travelers: are the classic road warriors
who need access to the corporate network and the Internet while traveling.

are employees who work one or more full days
a week from home and need to access the office network.

Home Workers:
work from home for short period of time, such as
evenings or weekends, in addition to their main activity at the work site.
  Small branch offices that require access to a central site or to each other to share data and information.
  The number of WAN users in the office and the data rates required by the offices's network connection vary widely depending upon the nature of the the work routines and application used. However, Basic Rate ISDN (BRI) is likely the minimum connection technology required.
Virtual Private Network(VPN)
  It is the connection method that distinguishes WAN and VPN.
WAN utilises private carrier the likes of Telstra, Optus and AAPT to connect remote site to central office networks whereas, VPN harness the power of the public network - the Internet. Instead of paying for the long-distance call connection the Internet is used as a cost-effective alternative.
If you are interested in WAN and VPN you are welcome to