A person with a well founded fear of persecution if he or she returns to their country of origin may apply for Asylum before the USCIS. Also, a person who is in removal proceedings may apply before an Immigration Judge for: Asylum, Withholding of Removal (must prove by a more likely than not standard); OR seek protection under the Convention Against Torture (must prove that you might be tortured if returned to your home country).
In order to apply for Asylum, the applicant must demonstrate that they will be persecuted if they return to their country of origin based upon their (1) political opinions, (2) religious beliefs, (3) nationality, (4) race, OR (5) membership in a particular social group. Being a member of a particular social group means possessing a personal characteristic that is unchangeable, such as being: female; homosexual; having a birth defect, etc, and not something transitory and changeable such as a hairstyle, clothing preference, etc.
The persecutor has to be either the actual government of the country, OR a group that is active within the applicant’s home country that the government either cannot or will not control. Examples of this may be hardline religious groups seeking to impose certain beliefs, drug dealers that operate violently without police intervention, etc.