The term “absolute path” is a rather arcane one. Using simpler speech, the “absolute path” is just the full listing of the location of a file or a folder/directory on a computer. It is sometimes known as the “full path.” The absolute path includes the complete location of the file or folder, including which drive it is on.
For example, on a Windows computer, the absolute path for a file might be:
C:\Windows\Users\Billy\docs\blogpost1.txt
Servers systems are required to know the absolute path for every file that it has access to in order to locate it. Each different operating system (Windows, Linux, MacOS, etc) uses a different syntax or way to write an absolute path.
There is also a term called “relative path,” which refers to the location of a file in relation to the current location. For example, the above file in Windows might be listed as “\docs\blogpost1.txt” if you are currently in the “Billy” folder.
The only time you need to know and use absolute paths in WordPress is when you are a developer and you need to reference the exact location of a file when writing code. To find the absolute path of files used for WordPress, you can write three simple lines of code in PHP and store that information on your web server for use as a reference.