Okay, so imagine you have to say goodbye to your friends because you're moving away. A farewell discourse is like the speech you would give them before leaving.
It's when someone is about to leave a group of people for a long time, and they want to say some important things before they go. This can happen in lots of different situations, like when a teacher is retiring or when a leader is stepping down from their position.
During a farewell discourse, the person usually talks about things they learned, experiences they had, and things they want the group to remember. They might talk about all the fun times they had together and how much they'll miss everyone. They might also give some advice for the future, like how to keep the group strong and successful even after they're gone.
It can be a little bit sad to hear a farewell discourse because it means someone you care about is leaving, but it can also be a really special moment because it shows how much that person cares about the group and wants everyone to be successful even when they're not there.