There is a good explanation of various micro-tasks' types and differences between freelancing etc:

https://www2.deloitte.com/content/dam/Deloitte/de/Documents/Innovation/us-cons-enterprise-crowdsourcing-and-growing-fragmentation-of-work%20(3).pdf

There will be micro-tasks like:

- label what is on the image (dog, car, pedestrian)
- select the sentiment of the tweet (positive/negative/neutral)
- put the item into a category

Therefore simple tasks, many times later the results are used for training AI algorithms.

Let me know if I can explain it better!
Petr