What do you mean by self-employed?
Self-employed is a broad description that many people who work now fall into. Generally, when the IRS talks about self-employment they could mean that you are an independent contractor or freelancer, you work on short-term contracts, or own your own business.
You can be considered self-employed even if you haven't formally launched your own business. Common examples of self-employment work includes driving using a rideshare app like Uber and Lyft, delivering items using an app like Instacart and Doordash, pet sitting or dog walking, and childcare services.
If you are a rideshare driver, you can find additional information at Taxoutreach.org/rideshare.