More than a third of Americans — 36 percent — say someone in their household owns a gun, according to an Associated Press-GfK poll conducted Jan. 10-14.
Millions use guns for hunting, sport and target shooting. Hunting guns include an array of shotguns and rifles of various types and sizes, including semi-automatics and the traditional bolt-action rifles. The prey and a hunter's personal preference determine the weapon and the kind of ammunition used.
Some people keep guns solely for protection. Carrying a concealed handgun is legal in every state but Illinois under certain conditions; for example, the gun owner might need to pass a background check first. Some states require safety classes. Some state and local laws, including in California and New York, make it difficult if not impossible to get a license to carry a concealed weapon. Illinois law bans carrying concealed weapons, but a federal appeals court overturned that law in December. The ruling is likely to be appealed.
Federal laws prevent the government from tracking how many guns are sold every year and who buys them, so there are no definitive statistics.
Roughly 310 million guns were owned or available for sale in the United States in 2009, according to a study by the nonpartisan Congressional Research Service. That's about 114 million handguns, 110 million rifles and 86 million shotguns.
Federal law requires anyone who buys a gun from a licensed dealer to submit to a background check. Convicted criminals and people who have been declared by a judge to be "mentally defective" are among those barred from buying a gun.
The Brady Campaign to Prevent Gun Violence says as many as 40 percent of all gun sales are completed without a background check. That's because sales between private gun owners and sales at gun shows are exempt under federal law.
Only California and Rhode Island require background checks for sales between private sellers and buyers. Colorado, Illinois, New York and Oregon require background checks for all sales at gun shows. Three other states, Connecticut, Maryland and Pennsylvania, require such reviews for handgun sales.
Obama has proposed a federal law requiring universal background checks for every gun sale.
It's the Constitution's Second Amendment that guarantees the right to "keep and bear arms."
The actual text reads: "A well regulated militia being necessary to the security of a free state, the right of the people to keep and bear arms shall not be infringed." What that means has been debated and argued for decades.
The Supreme Court in 2008 ruled that Americans have a right to firearms, regardless of whether they serve in a militia. The justices also have signaled that some gun regulations could survive legal challenges, but they haven't resolved which ones are permissible.
Associated Press writer Connie Cass contributed to this report.
Follow Alicia A. Caldwell on Twitter at www.twitter.com/acaldwellap
Copyright 2013 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.