If you've applied for certain immigration petitions or applications (green card, visas, naturalization, etc.) you may need to get your biometrics taken. After USCIS receives your application, you'll receive notice of your biometrics appointment a couple weeks later. You'll need to bring your biometrics appointment notice along with your photo ID. You'll then get your photograph and fingerprints taken.
Speak with an immigration attorney if you need legal advice.