This tab allows to set navigation and sorting options. There are two sets of options, one applies to the start page of your 'shop' the other to all other deeper pages.
When setting the group on option to on or setting it to one of the database fields, the component will only show a single item per value of that field. When set to on the field from the first menu level will be used.
example: if you set the value to 'merchant' (=feed name) to component will show a single item of each merchant on the homepage. This gives a more divers presentation.
Another purpose of the group function is with siblings, assigning for example the 'ean code' to a Select field and then grouping on this field will only show a single product with that ean code. Then siblings can be used to show the rest in a price comparison.
With group other pages (svn:1433)set to yes not only on the first page items are grouped but on all other deeper pages as well, intented usage is with siblings.
With group other pages set to smart grouping is automatic turned of when there is nothing to group. For example there is just on merchant left.
On the fashion demo the group on is set to Select1 (the gender), now for example a page like underwear will only show 3 items: one for each gender. While men's underwear will show all products since there is nothing to group on: only one gender.