History
Jason Donenfeld, like many of us, was tired of everything breaking. In 2015 he decided: "Enough bloating the code, let's build a VPN that simply flies." WireGuard was created as a protest against the complexity of OpenVPN and IPsec.
He wanted the protocol to work as easily as SSH: you have keys — you have a connection. Initially it only worked in Linux, and many called it a "toy." But in 2020 Linus Torvalds personally merged it into the Linux 5.6 kernel — the highest sign of trust in the open-source world.
Advantages
WireGuard is simply fast. Like a Bugatti Veyron on an empty highway. Its codebase is only 4,000 lines (versus 70,000+ in OpenVPN). Because of this it's lightweight — it runs right in the kernel, without wasting time on constant context switches. The speed gain over OpenVPN is often +50-100%. It uses only the most modern ciphers: ChaCha20 and Poly1305, considered virtually unbreakable.
Disadvantages
The first downside is privacy issues by default. WireGuard stores your IP on the server until restart. The second is detectability. It strictly uses UDP and has fixed packet headers. For a Deep Packet Inspection (DPI) system, WireGuard looks like a person in a suit with a neon sign: visible immediately.
Summary
Choose WireGuard if you need speed for 4K video or gaming, and your ISP doesn't block it. It's a sports car: sharp, bold, powerful. But for off-road driving (countries with strict censorship) it doesn't work unless specially disguised.