Lite and Pro account users have the ability to perform a deep search by selecting the drop down before pressing "Search":
What does Deep search do?
A standard search goes 2 levels deep into People Also Ask results and on average returns approximately 25 questions.
A deep search goes 3 "levels" deep into People Also Ask results and on average returns approximately 100 questions.
What does "4 credits" mean?
A deep search will cost you 4 searches, as opposed to the regular 1 search credit deducted from completing a search.
It is cheaper and faster to get questions using deep search than manually repeating searches or exploring nodes within a standard search result.