This information puts you on notice that a marriage that has lasted less than two full years on the date that a person is adjusted pursuant to a form I-485 or upon the date of entry into the U.S. with an Immigrant Visa, the new immigrant will be a "Conditional Permanent Resident" (CR). The CR status is applies, if the marriage creating the relationship is under 2 years, to the spouse and stepchildren of a USC or LPR I-130 Petitioner. The CR is issued a greencard with a two year validity period. Within the final 3 months of the card's validity you file a form I-751 to lift/remove the conditions upon a showing that the marriage was bona fide and not merely a sham/fraud just to get a greencard.
INA 216 [8 USC 1186a] is the codification of the Immigration Marriage Fraud Amendments of 1986, as amended.