Everyone has hit it: a site won't open, saying access denied. Most often it is a regional block or an IP block. And almost always a proxy solves it. A proxy gives you an address from another country — the site sees the proxy IP, not yours, as if you were sitting in Germany or the US. That is how bypassing blocks works without complex setup.
An important nuance: take a proxy from the country where the site is available. Many services need a specific region — a country filter helps. And do not forget DNS: if domains resolve on your side, your provider sees where you go. SOCKS5 with proxy-side DNS resolves that too.
Proxies for bypassing blocks are also useful at work: testing geo-targeting, accessing foreign services, checking ads. The key is a live pool: a dead address opens nothing.