pwd is a simple command that outputs your Present Working Directory (apparently the command stands for Print Working Directory), or whatever folder you've
cded into. This is used in backticks, which instructs bash to execute
pwd and then pass it as an argument to
./install_***.sh. All it's doing is simply telling the installation script where you are on your hard drive. If you were in the folder, for example,
/home/billy/Documents when you executed the script, this would be the exact same as executing
It's not a placeholder put in by the documentation or anything, it's an actual command.
As mentions in comments by @ThomasWard, backticks are, at least sort of, deprecated, and you should use