Honestly, as an engineer, I have never seen them do anything.
Tenure: means get permanent job.
part time instructor usually means the person has another job, often in that field,or related. But he could be a beekeeper, who knows?
Where can you learn computer science by volunteering? Hmmmmm. Have you tried to do some website design on your own, and once you learn it, do it for non-profits? I am the area director for Girl Scouts, and I have a 6th grade boy who is doing website design for our troops. Yes, he is learning about computer science. But caution on this, website design is a very small part of computer science. Have you thought of buying some used texts from your nearest college bookstore?
This website was designed initially by a middle school boy 15 years back, as a way of helping his classmates. Nowdays, he is a full time commercial computer scientist. Here is a copy of the website then (Broken Link Removed)
He named the website Jiskha, after his dog.
So just get started, you never know where it will lead.
part-time = does not teach as many classes as full-time instructors do
tenure-track = the instructor teaches full-time and can be considered for tenure
Specifics for all these positions vary depending on state and school.
You could volunteer just about anywhere computers are used for keeping track of things ... food donations, pets, etc.