It is most likely your local taxes. PA collects both an earned income tax (the rate is based on home and work locations) and LST (flat rate). Keystone collects these taxes for local municipalities. Usually, your employer withholds these taxes, and you just have to fill out the form stating you are not entitled to a refund, nor owe any taxes.

https://dced.pa.gov/local-government/local-income-tax-information/