Filters are a way to ensure actions get performed only on the items you want. With filters, you set a specific condition to get to the granularity you need.
For instance, you can set up a filter to only capture emails that contain a specific subject line or only customers who purchase a specific product. So when the data from your Zap meets the conditions of a filter, it proceeds to the next action in your Zap. If a filter stops an item, then no further actions are performed.
If a filter does not pass, it does not count as a task, and no other action will run that would count as a task either.
Learn how to set up filters for your Zap.