A gouge is a profile of the quirky things a specific DPE is known for asking, or the scenarios they often give an applicant.

After passing a private pilot exam to be able to fly an airplane in the first place, hopeful crop duster pilots must then pass a commercial pilot exam to earn the right to be paid for their skills.

The typical certifications one should expect to get are the Student Pilot Certificate, Private Pilot's License (PPL), Instrument Rating (IR), Commercial Pilot's License (CPL), Multi-engine ratings ...