Ports are where old games designed to run on one platform such as DOS are converted to run another platform such as Linux. They can occur when the source code is released, for example Doom in 1997. Developers then begin to adapt the code, taking advantage of modern enhancements such as the SDL libraries which allow for use of modern game controllers. You can find out more, including a list of notable ports, at the following Wikipedia link.
https://en.wikipedia.org/wiki/Source_port
You can follow my tutorial on how to install the Wolfenstein 3D port, Wolf4SDL, at the link below.
http://dosonthepi.blogspot.com/2015/01/install-wolf4sdl.html
It’s worth comparing the performance of the port and Wolfenstein 3D run in DOSBox (you can find a link to a tutorial on how to do this at my blog).
I’ll post more tutorials on the blog. If there’s any ported game you’re interested in then let me know.