It's a tax-reporting form that eBay is required to send to sellers who have more than 200 transactions worth over $20,000 in the calendar year (and to the IRS). Some states have set lower thresholds, but you're in Pennsylvania which has not done that, so eBay will produce a 1099-K for you only if they processed over $20K for you last year. For 2022, the federal threshold is $600, so you'll get one next year.
