Each row represents 1-many Filters or Value Fields (for simplicity's sake, both filters and value fields will be referred as elements). 

Ordinary elements

The elements are grouped by data, the element works with. 

An example of this grouping is filters working with the keywords Meta data field:

The Details panel for this filter:

In this grouping, the two filters are a FreeText filter and an InList filter. The relationship between these two keywords filters is the same as with any other single filter, ie the logical grouping of filters has no impact on the search itself.

Group

An exception of this grouping is when a filter is a Group. In this scenario the group's filters are grouped together even if the data, which they work with, is different from one filter in the group to another. 

The reasoning behind this is that the Conditions in the group will only make sense if the group's filters are placed together.

Example:

Greyed out rows

Some filters and value fields may not be edited or deleted. This is signified by the rows being greyed out:

And The Details panel will be:

If a row represents more than one element, and one of the elements is uneditable, but others are editable, then the row is not greyed out:

And The Details panel will be: