What is MongoDB Aggregation and when should you use the Aggregation Pipeline?

I'm learning MongoDB and often hear about the Aggregation Framework and Aggregation Pipeline for processing data. I understand it's used for advanced queries, but I'm not sure how it differs from regular find() queries or when it's the better choice.

Can someone explain what MongoDB Aggregation is, how the Aggregation Pipeline works, and the purpose of common stages like $match, $group, $project, $sort, and $lookup? A simple real-world example demonstrating data analysis or report generation would be very helpful.