When you view or edit a text (.txt) file in a text editor like Notepad, you're most often opening a file in ASCII encoding that uses the ASCII binary values for common letters, numbers and punctuation. The only values allowed in that kind of file are lowercase letters, uppercase letters, numbers and punctuation.

You can also view or edit binary files, like executables (.exe), but you typically need a hex editor. If you tried to open a binary file in a plain text editor it wouldn't know how to handle all the binary values that are not part of the standard ASCII set of letters, numbers and punctuation.

Hex editors show the data in hexadecimal format. They convert the binary data to numbers from 0 to 15 where the numbers 10 to 15 are replaced by the letters A to F. Often to make it clear people are talking about the hex number they add "0x" in front of the number. So, 0 becomes 0x0, 9 becomes 0x9, 15 becomes 0xF, 16 becomes 0x10, and 255 becomes 0xFF. This is an efficient way for people to work with binary data because 16 is 2^4^ or 222*2.

Within binary files, there will still be a lot of sections that are in ASCII. For example, any error messages that have to be printed out for the user to see, like "this program cannot be operated in DOS mode".

Razor 1911 is an infamous cracker group that has been around for decades. They often "sign" the programs they crack by putting "Razor 1911" inside the files, in a way where you can see it if you open it with a hex editor, but so it doesn't affect the program.

So, what this is suggesting is that a program that Rockstar has released on Steam is not something they built themselves, but they're actually distributing a cracked version that was released by Razor 1911.