The mass shooting of 17 people at a Florida high school in February has reignited the long-running debate over gun laws in the United States. Here is a look at some gun rights and gun control groups in the U.S.:
Prominent gun rights groups
National Rifle Association
The NRA, which claims 5 million members, is one of the country's most powerful lobbying groups for gun rights. Founded in 1871, it seeks to educate the public about firearms and defend U.S. citizens' Second Amendment rights. It has directly lobbied for and against legislation since 1975.
The Center for Responsive Politics, which tracks data reported to the Federal Election Commission, says the group has made nearly $23 million in direct political contributions since 1989.
Gun Owners of America
Gun Owners of America was formed in 1975 to protect the rights of gun owners. The group says on its website that it sees "firearms ownership as a freedom issue."
The group has built a nationwide network of attorneys and says they've fought court battles in almost every U.S. state to protect gun owners' rights. It says it has also worked with members of Congress, state legislators and local citizens to protect gun ranges and local gun clubs from closure by "overzealous government anti-gun bureaucrats."
National Association for Gun Rights
NAGR was founded in 2001 and claims on its website that it is the fastest-growing gun rights group in America. The group says that it has 4.5 million grass-roots activists and that it focuses on educating gun owners about state and federal legislation that affects their gun rights
One of its main efforts is to advance "constitutional carry" legislation, which would allow people to carry weapons without first obtaining a permit. "Law-abiding people shouldn't be forced to get a government permission slip to exercise their right to self-defense. No one should be treated like a criminal simply for wishing to carry a firearm in defense of themselves or their family," NAGR says on its website.
The group also differentiates itself from the NRA. "Unlike the NRA, NAGR believes in absolutely 100% NO COMPROMISE on gun rights issues," it says.
Prominent gun control groups
Brady Campaign to Prevent Gun Violence
The Brady Campaign works to elect public officials who support gun control legislation and to increase public awareness of gun violence.
Named after James Brady, President Ronald Reagan's press secretary who was shot and nearly killed in a presidential assassination attempt, this group scored a victory in the 1990s with the federal assault weapons ban. (Legislative efforts to renew the ban failed, and it expired in September 2004.)
The group's stated mission is to cut the number of U.S. gun deaths in half by 2025, partly by working to implement background checks on all gun sales. In addition, the group wants to lead a new national conversation and "change social norms around the real dangers of guns in the home, to prevent the homicides, suicides and unintentional shootings that happen every day as a result."
Giffords was founded by shooting victim and former Democratic U.S. Representative Gabby Giffords of Arizona and her husband, former astronaut Mark Kelly. It was originally known as Americans for Responsible Solutions.
Giffords' stated goal is to "research, write and propose policies that make Americans safer and mobilize voters and lawmakers in support of safer gun laws."
Giffords, who was shot in 2011, announced the formation of the group following the mass shooting of 20 children and six adults at Sandy Hook Elementary School in Newtown, Connecticut, in December 2012.
Giffords and Kelly call themselves Second Amendment supporters, but are also committed to lobbying for expanded background checks, stiffer penalties on gun trafficking, and funding for research on the causes of gun violence.
Everytown for Gun Safety
Everytown for Gun Safety was founded by former New York Mayor Michael Bloomberg. Formerly called Mayors Against Illegal Guns, the group lobbies for gun control legislation on a local and federal level and provides a support network for gun violence survivors.
On its website, the group says, "For too long, change has been thwarted by the Washington gun lobby and by leaders who refuse to take common-sense steps that will save lives."
The Center for Responsive Politics, which tracks data reported to the Federal Election Commission, says Bloomberg gave a total of $28 million to outside spending groups during the 2014 cycle to push for changes in gun control.