Some software doesn’t check if it’s purchase, so in that case one just needs the files or installer. If the software does check, one would find a vulnerability in the code that is checking if the game or software was purchased and work around the check.

For old consoles like the ps1 you would install a chip that allowed it to read burned discs

Some software allows you to download effectively the entire program, and only authenticate with a key right at the end, rather than needing a key up front. This can often be done so the user gets limited access to the software on a trial basis, and then pays for the full version later. Given this, if you can trick the software into thinking it's authenticated, then you could pirate the software.

You used to be able to pirate the software using an app called a key generator, or Keygen, which was a mini program that could generate license keys for the software so that people could avoid paying.

In recent years companies have added additional layers of security to try and make it harder to pirate software. This can take the form of various Digital Rights Management tools (DRM), which could include having to authenticate the install by having an account with the company that has you as a registered purchaser. This makes it much more challenging to pirate the software vs simply having to provide a key that looks correct.

If the game has no anti-piracy protection - then it is exactly how it works: just copying files is enough.

If there is a protection - the game will try to check if you bought the game. However, the game runs on your computer, for which you have absolute control over! Yet.

• If the game checks DVD disk, you can install a fake DVD driver. It will pretend, that there are a disk installed and will allow a program to read it - but will actually read data from a file. Then just copy data from the real DVD to a file.
• You can inspect the program's memory to figure out what its doing, and then edit the EXE to change its behavior. Yes, it contains the dreaded "machine code", the language of the CPU - but it is possible to just learn it (it's description is published on the Internet). You can also use helpful tools, that will convert it into a more human-readable form. The goal is to find a place where the game does a check, and replace it with "always pass".

Hacks, cracks, and jacks.

Hacks are tools that allow you to take a straight copy/paste and edit some portion of the code so that a copy check always passes. (Breaking the lock)

Cracks are tools that allow you to use other programs to create codes or keys that will pass any verification check (think of a key-duplicating machine at a hardware store)

Jacks: straight up copies of stuff that doesn't even have a lock on it, or one that's so simple it can be bypassed just by pushing hard enough.

But, everything starts with a straight-up copy/paste of the original software.

Informational: An interesting DRM invention in the PS1, was the "bounce" that all PS1 discs had at the beginning of the read.

The lazer would follow the read path of the disc, and watch for a specific wobble. If the wobble was there, the DRM passed, and the disc would load.

You would often hear people touting that you could place a ps1 disc in the tray to get it started (with the "lid-closed" pin held down with tape), then swap out the disc to a burned one to play it. This would work because of that drm system :D

You can basically just copy and paste it, it’s just a specialized executable (.exe) file.

What people are mentioning about cracks and hacks are just fancy ways of saying “tricking the system”

Easy example would be an old game that came with a CD key like Diablo. All it did is check if the game was installed and a valid key has been put in previously. Cracks/hacks basically make the last step moot in one way or another. It’s really no different than if you used your friends key just…. Thousands of people using the same code (thus why a lot of the time you could not go online with these games since some games would do additional checks once connected to the internet)

You remove the tiny portion of code protecting it, or find some sort of work around. Like the only thing keeping your house safe is the lock on the door. So you can turn the exe to code, find the lock, and remove it. Turn the code back to an exe, and voila!