GMC Envoy P0171 Code: What Does 'Fuel Trim System Lean' Mean?

I own a GMC Envoy and have recently received the diagnostic trouble code P0171, which indicates a 'Fuel Trim System Lean' condition. I'm trying to understand what this exactly means in simple terms. The definition suggests that the fuel mixture on Bank 1 of the engine is too lean—meaning there's not enough fuel or too much air. This can lead to poor performance, reduced fuel efficiency, and potentially engine damage if unresolved. Possible causes include a dirty or faulty Mass Air Flow (MAF) sensor, vacuum leaks, a malfunctioning fuel pressure regulator, or defective fuel injectors. I'd like to know what year and engine size my GMC Envoy has—does this affect how the P0171 code is interpreted? Any insights would be greatly appreciated. Note: For community safety and to prevent spam, please avoid sharing personal email addresses in forum posts.