In some situations, you may want to make a more complex selections of events.
Then instead of having to select events with the mouse, the Logical Event Selector may be a handy tool.
For example, you may want to select all note between bar 9 and 17 that are between C3 and C4 and with a velocity below 87 but with a length greater than 1.5 beats.
Now this is very difficult to do with the mouse, but it's a piece of cake for the Logical Event Selector.
The Logical Event Selector preserves an existing selection so you could first make a selection, manually or also using the Logical Event Selector.
Then you can use the Logical Event Selector to unselect a clip of the selection. This could be called making layered selections.
If you want to use criteria for Value 1/2 then you also need to define the event type because Value 1/2 depends on the event type.
More concrete: If you want, for example, to select all notes between C4 and C5, you also need to set "Type Equal Note" so that the Logical Selector knows it's about notes and so that the criteria for Value 1/2 can be entered in their relevant format, i.e. as note keys in this example.