What is 'Ring of Fire' behind Taiwan's strong earthquake?

Taiwan's 7.4-magnitude earthquake was its strongest in 25 years. Taiwan sits on 'Ring of Fire', a horseshoe-shaped zone around the Pacific Ocean which is "the world's most seismically and volcanically active zone", according to USGS. The nearly 40,000-km arc extends through New Zealand, Japan and off the west coast of mainland Asia, around down the west coast of the Americas.