The begin new entry command creates a new scope, and adds it to a list in the current scope every time its executed. The list name can be changed by editing it in the template pane.
If a list by that name doesn't exist in the current scope, a new (empty) one is created before adding the scope to it. The current scope is set to the new scope temporarily while executing all children of the list command.
Typically, the begin new entry command will be used inside a selection with multiple elements. Since a new scope is created each time the begin new entry command is executed, this should create a list that's the size of the parent selection.