PATH is an environment variable on Unix-like operating systems, DOS, OS/2, and Microsoft Windows, specifying a set of directories where executable programs are located.
[1] On POSIX and Unix-like operating systems, the $PATH variable is specified as a list of one or more directory names separated by colon (:) characters.
System administrators as a rule do not include it in $PATH in order to prevent the accidental execution of scripts residing in the current directory, such as may be placed there by a malicious tarbomb.
On DOS, OS/2, and Windows operating systems, the %PATH% variable is specified as a list of one or more directory names separated by semicolon (;) characters.
Some programs may add their directory to the front of the PATH variable's content during installation, to speed up the search process and/or override OS commands.