VPN stands for Virtual Private Network. If the VPN app on your phone and pad is on, all the addresses you ask your internet to visit (e.g. view GN website, send an email via your email provider, view your online banking accounts etc.) are encrypted/scrambled by the VPN software. Your WiFi router just routes your traffic to your internet service provider which forwards your request on to the VPN servers. The VPN server decrypts the address of the website you want to visit and delivers your request to, say, the GransNet servers. This means that your internet service provider never actually sees which sites you access.
You are only aware that you have been using a VPN because you see that it is not enabled on your devices at the moment.
Usually you have to pay for the use of a VPN although there are a few free ones. I pay for a password manager and that comes with a VPN.
Do you need to use one? My reasoning is that it depends on where you are. If you live in a busy area, go shopping and use your phone to pay for things and check on-line banking (places that are higher risk of your WiFi messages being 'hacked'), I'd say yes, it is a good idea. I don't use a VPN when home but turn it on if I'm having coffee in Neros and I want to check my emails.
I should say that some networks block the use of VPNs. My public library WiFi will not allow me to connect to it if I'm using a VPN (customers sit and browse porn apparently). NetFlix (among many streaming platforms) also blocks VPNs
If you use mobile data on your mobile phone (mobile data is not WiFi), I wouldn't bother with a VPN, it's much harder to hack phone networks, although not impossible. However, mobile data is only OK if you have a good mobile signal.
Somewhere among the apps on your pad and mobile, you should find a VPN app that you can turn on and off.
