Cross tables are table where facts are divided on the basis of dimension values.
for example we have sales for every month. then, if in our database we load sales amounts as a separated field for every month as
Product Jan Feb Mar etc
a 100 200 300
So, basically we have 1 single fact as sales amount here, and jan-dec are dimension memebers of month dimension but we are creating different fields for every dimension member and treating them as different field.
Loading data this way, makes it difficult to properly aggregrate the data over different dimensions and difficult to do analysis.
So, we convert this crosstable into a normal table.
crosstable (Month, Amount)
then we will get the same table as
Product Month Amount
a jan 100
a feb 200
a mar 300
I hope you understand now, what is crosstable. let me know if it solves your concern.