Spouses and children of US citizens are considered to be immediate relatives. Immigration for them differs significantly, as not only they are not subject to annual quotas, but also some of their immigration violations may be "forgiven." Adjustment of status (getting the greencard while in the US) is more likely to be available to them, which is often a much faster process than consular processing (getting greencard while outside the US).
There are different categories for relatives of US citizens and greencard-holders. Unless an immediate relative of a US citizen, the foreign national beneficiary is subject to annual quotas, resulting in wait for an available visa number, sometimes up to 15-20 years. Below is the list of catogories, and the maximum number of immigrant visas given each year.
First: (F1) Unmarried Sons and Daughters of U.S. Citizens: 23,400 plus any numbers not required for fourth preference.
Second: Spouses and Children, and Unmarried Sons and Daughters of Permanent Residents: 114,200, plus the number (if any) by which the worldwide family preference level exceeds 226,000, plus any unused first preference numbers:
A. (F2A) Spouses and Children of Permanent Residents: 77% of the overall second preference limitation, of which 75% are exempt from the per-country limit;
B. (F2B) Unmarried Sons and Daughters (21 years of age or older) of Permanent Residents: 23% of the overall second preference limitation.
Third: (F3) Married Sons and Daughters of U.S. Citizens: 23,400, plus any numbers not required by first and second preferences.
Fourth: (F4) Brothers and Sisters of Adult U.S. Citizens: 65,000, plus any numbers not required by first three preferences.
You may check the current visa bulletin here