Penal servitude is when a person is sent to a special place to work as a punishment for doing something wrong. It's like the time-out corner of the adult world.
Let's say you took a cookie from the cookie jar even though you knew you weren't supposed to. Your mom might say, "No more cookies for you and go to your room for 10 minutes," right? Well, imagine if you took a cookie from the cookie jar and your punishment was to go to a place where you have to work really hard for a certain amount of time.
That's what penal servitude is - a punishment where you have to work hard, often doing things like digging ditches, chopping wood, or making clothing for other people. It's usually for a long time, like a few years, and you stay in a special place called a prison or labor camp with other people who are also being punished for doing something wrong.
The hope is that by doing hard work, you will learn your lesson and not do the same thing wrong again. So, it's like a really serious time-out that helps people learn from their mistakes.