VPN is virtual private network which protects your real identity from internet like from any website you visit or from shipping site, you get the idea right! VPN actually creates an ip address which is different from your ip address and when you using the internet all your internet traffic goes through the vpn ip address.

Normally of you use internet your ISP internet service provider knows everything you do on the internet because all your internet traffic goes through the ISP.

for example, if you try to open a website you open the browser and search using any search engine you like and your ISP will give you access to use the internet also your ISP will give you an ip address and through that IP address all your searches and internet traffic will be done. Here your ISP can see what you searching and if your ISP can block you from visiting certain sites.

Now if you use a vpn, your vpn provider will give you an ip address and when you surf the internet using vpn, all your internet traffic is encrypted means your isp cannot see your searches or which site you visiting, so yout vpn is masking your internet traffic from your ISP.

Hope this gives you enough(basic) information about vpn. always use open source software.