Conditional residency is granted to certain categories of aliens before they are granted the right to live in the U.S. on a permanent basis.
There are two types of conditional residents that are allowed into the US. The one most people are familiar with is by being married to a United States citizen. Many people assume that if they adjust status based on marriage to a U.S. citizen, they will immediately become a permanent resident. This is not always the case, however. Many non-U.S. citizens are given a conditional residency within the country instead.