You may need to install this if you want to compile and install NGINX from the source. An error requiring it may look something like this:
./configure: error: the HTTP XSLT module requires the libxml2/libxslt libraries. You can either do not enable the module or install the libraries.
To install libxslt on Ubuntu, issue one of the two following commands on the terminal:
sudo apt-get install libxslt-dev OR sudo snap install libxslt