Why is it possible to bypass dangers of hotspots and public networks with VPN?

The use of hotspots and public networks involves immense possibilities for third parties. For professionals, it's easy to view data traffic and get access to confidential information, such as business emails or account information being sent through public connections.
With a VPN service you can protect yourself against such attacks easily. The servers of your VPN provider handle every request and masks it by using a non-traceable IP adress of the provider to establish any requested connection to websites etc. and forwards it back to the user.
The connection between your computer or mobile device and the requested servers are highly encrypted - usually at least 128-bit - so that all traffic is tap-proof.

While using a VPN connection, you can use public networks without having to worry, because your in- and outgoing traffic is encrypted and not available for third parties.