[Koha] Need help on catalogueentry table

[fabien]

Hi,

I'm currently importing data to Koha in order to put our library online. I am 
converting an old database via Access and ODBC to import it into Koha. I
would like to know a bit more about the way subjects are connected.
I've done an import into the bibliosubject table so far and it works but I
would like my subjects to be interconnected and I guess the table
catalogueentry does it.
Most of the fields are pretty obvious (or so it seems) but I have a question
about ENTRYTYPE, which is a varchar(2), what does it refer to?
I guess that each book is described by is biblionumber and the subjects go in
the fields catalogueentry, see, seealso, seeinstead, am I right???...
Could someone give me a few explanations on this?
I would also need to know what classification in biblioitem is... Is it a
general category like non fiction or something like this or ....???? Is it
this classification that shows on the advanced search /cat page??

Thanks for any help you could provide,

Fabien