By default, Behold uses its Auto Organize capability to determine the main people in each file. Usually it will select a pair of spouses and list them on two lines. All the relatives of each person make up that person's Family. Relatives include half-family and step-family, but do not include relatives through marriage other than the person who married into the family.
The checkmarks indicate which families will be included in the Everything Report. Unchecking a family is a simple way of excluding it without removing it. This way, the families you often organize around can stay on the Families page so you don't have to keep searching for them whenever you need them again.
There are two special family groups that are always at the bottom of the Families page: "Others Related Through Marriage" and "Everyone Else".
You cannot remove these groups and you cannot move them up or down. But you can select or deselect them and change their ID.
These give you the capability of including the other people that are not in the family groups you have selected. If Others Related Through Marriage is not selected, then those people will be included in the Everyone Else group if it is selected.
To make it easy for you to change whether RM and EE are selected or not, the toolbar on the main Behold window has two icons that you can use:
Here you see RM as not selected (flat) and EE as selected (pushed in). By clicking with your mouse on one of these icons, you will change its selection (without having to come into the Organize window) and Behold will immediately recreate the Everything Report with the new setting.