What is Telegram and why was its CEO arrested in Paris?

Pavel Durov, the founder and CEO of the messaging app Telegram, was arrested in Paris over the weekend over allegations that his platform is being used for illicit activity such as drug trafficking and the distribution of child sexual abuse images.

Durov, who was born in Russia, spent much of his childhood in Italy and is a citizen of France, Russia, the Caribbean island nation of St. Kitts and Nevis and the United Arab Emirates. He was taken into custody at Paris-Le Bourget Airport in France on Saturday after landing from Azerbaijan.