Immediate relatives of u.s. citizens
Unlike any of the other categories, visas for immediate relatives of U.S. Citizens are not limited in number. In the immigration context, "immediate relatives" refers to spouses, unmarried children under 21 years of age, and the parents of U.S. Citizens that are over 21 years of age. If you fit into one of these categories, you can apply for Permanent Residency without being subject to the long waiting periods that other family members of U.S. Citizens or Legal Permanent Residents face.
Immediate relatives of legal permanent residents
If you are the spouse or unmarried child of a Legal Permanent Resident (LPR), you may have your LPR relative file a petition for you, and when a visa becomes available under your particular preference category, you can apply for your green card!
*REMEMBER, same sex married couples are afforded the same immigration benefits as opposite sex married couples.