I need a crash course in the handicap systems. They are designed to compare two different boats on a "time over distance" basis, correct?

In gathering the data from a bouy race, they would need the elapsed time the boats finished as well as the length of the course, right?

And if it's a one design fleet, this information is not usually kept (only finish position), which tends to screw up calculations?

It seems so simple in theory, but those earlier posts are way too complicated. Are they crunching all those numbers to determine a provisional rating rather than a compliation of historical data?