ahahahahahha,.............. funny but a Great Question
The answer is really simple, bro. They're running "Console Emulators"..... so please google this if you want to find out more.
But First of all, No there is no emulator for the newer PS4 console. Orbital hopes the be the PS4 emulator of choice but they're in the early stages. There seems to be some life for XBox One emulators but I don't know much about this. I have heard of people playing Red Dead Redemption 2 on their PC through an emulator though so it must be an XBox One emulator.
The thing of it is, you don't need a very good PC to run emulators for older consoles but you need a good PC to run PS3, XBox 360, Wii U, Switch, and XBox One emulator programs.
Each of these emulators have funny names too, like Yuzu is the Emulator for the Switch, RPCS3 is the Emulator for the PS3, Dolphin is the emulator for the Gamecube and Wii.
You get to play games for free and they'll work with an XBox controller.
You can program the settings and often times the game will look better on the PC than it ever did on the console. Zelda Breath of the Wild played on the Cemu Emulator for the Wii U looks better on a good gaming PC than it does on the Switch..... and no that's not a typo. I meant to say a Wii U emulated game looks better than it does on the Switch.
You're not paying for the games which shafts the developers. You're basically downloading a pirated copy of the game.
These emulators are subject to litigation and they could be removed at any time.
The emulation process is difficult and there aren't that many games to choose from. Only 1/3 of the PS2 library is available to play on emulators. It will be years before the PS4 emulators have a decent library.
Some games don't run that well.
NO, there is no way to turn a Gaming PC into a console. You can hook your PC up to a TV set, download launch programs like Steam, Origin(EA), UPlay (Ubisoft), Battlenet (Blizzard/Call of Duty), etc, and then you can game on an XBox controller the same way you would with a console. You can even buy a Wireless XBox One controller that has a USB stick which is meant for the PC. I've done this in the past but many PC gamers prefer to stick to a keyboard and mouse because sometimes this gives them an advantage in certain games.