Alright kiddo, do you know what numbers are? Good. Now, let's say we have a very big number, like 10,000, and a very small number, like 0.0001. These are called magnitudes.
Subminor means something that is located in a smaller magnitude than something else. Think of it like a little ant (subminor) walking on a big elephant (supermajor). The ant is so small compared to the elephant, which is supermajor in size and magnitude.
On the other hand, supermajor means something that is located in a bigger magnitude than something else. So if we compare a tiny grain of sand (subminor) to the entire beach (supermajor), the beach is much bigger and has a supermajor magnitude compared to the sand.
It's like comparing big and small things - subminor refers to the smaller thing, and supermajor refers to the bigger thing.