@tigerdragon The six college system at UCSD is based on Oxford University. Many people describe it like Hogwarts, where you have four different houses that you dorm with and have different activities with, but you still take the same classes. Each college is different based on their pre reqs-- for example, ERC has to learn a foreign language I believe. The Jacobs School of Engineering is just what all the engineering majors are under.
Undeclared means that he was not accepted as his first choice major (assuming he didn’t put undeclared). He will have to find a major to pursue, fulfill the prereqs, and have the counselor approve him to transfer into whatever major he decides to declare. He must declare before his third year. I believe all, if not most, engineering majors are impacted and are therefore extremely hard to transfer into.