You can display only the data whose value of the Distribution column match the condition that is specified by this setting.
Here are descriptions for each radio button.
You can specify a distribution with the distribution dialog that will appear by clicking the "..." button.
On usage of the Distribution dialog, refer to Section 2.2.4 ( page).
Hint : A search whose condition is specified only by the distribution can be done by choosing an item from the Distribution radio buttons on the Display Condition panel while the Search Key entry is empty.