Main difference between a proxy and a VPN is that a proxy is at an application level (http/https). VPNs tend to be a "all in one" solution where you connect, and all data/traffic is encrypted and anonymous.
Proxies on the other hand don't hide all data flowing from your device. If you have a list of proxy IPs/ports and add them to an application, that application will send requests via those proxies, keeping that specific request/connection anonymous - all while you can be browsing the net or watching YouTube on you PC as usual, with your normal IP.
Easy way to think of it is:
If you want all your data to be anon, use a vpn.
if you need to hide your IP because you are brute-forcing logins to a website/app - use proxies.
Proxies are cheap and easily obtainable, but they're much less secure than a VPN.
Hope this helps!