What is an AR-15 and how did it become so popular and ubiquitous?

The rifle is a central symbol in the US gun debate - but will Trump's assassination attempt change the way it's seen?

Images of AR-15 semi-automatic rifles are everywhere in American public life: Republican congressmen sport lapel pins shaped like AR-15s. Confederate flags with the silhouette of an AR-15 and the phrase come and take it" flying outside the Capitol during the January 6 insurrection. They're also used to evoke the need for stricter gun safety measures.

On Saturday, the AR-15 re-entered American politics in another way - as the weapon used in the assassination attempt of former president Donald Trump.