What are MANPADs, the shoulder-fired missiles China reportedly supplying to Iran?

Amid the ongoing war with Iran, US intelligence sources told CNN that Tehran could soon get 1,000+ MANPADs from China. MANPADs, or man-portable air defence systems, are shoulder-fired, infrared-guided anti-aircraft missiles carried and operated by a lone soldier. They are easy to conceal, transport and use and are difficult to counter. The missiles travel at twice the speed of sound.