I'm a bit confused. I've never programmed databases, though i have a lot of programming experience.

The student made a structure that can be seen as a unit or table in a database. Is the database not clever enough to synthesize a unique id? Why does the programmer need to care about keys?

It is clear that the end user will not know anything about a key, it might be a byte offset in a file or a memory pointer. Why does the programmer need a key?