Full of busy, energetic activity and movement, especially with many people.
“The picture shows a bustling street market full of vendors and shoppers.”
“It's a bustling downtown area with people walking in every direction.”
Use this word to describe an overall busy scene, like a marketplace or city street, in your Task 3 introduction — it's a great high-level word for setting the tone of the whole picture before you describe specific details.
Synonyms: busy, lively, crowded