The one on the bottom is Sojourner, the one on the left is a Mars Exploration Rover (two were launched, Spirit and Opportunity), and the one on the right is Curiosity.
Sojourner was the Mars Pathfinder robotic Mars rover that landed on July 4, 1997 in the Ares Vallis region, and explored Mars for around three months. It has front and rear cameras and hardware to conduct several scientific experiments. Designed for a mission lasting 7 sols, with possible extension to 30 sols, it was in fact active for 83 sols.
Spirit and Opportunity were sent to explore the Martian surface and geology; both landed on Mars at separate locations in January 2004. Both rovers far outlived their planned missions of 90 Martian solar days: Spirit was active until 2010, while Opportunity is still active in 2018, and holds the record for the longest distance driven by any off-Earth wheeled vehicle.
Curiosity is a car-sized rover designed to explore Gale Crater on Mars as part of NASA's Mars Science Laboratory mission (MSL). Curiosity was launched from Cape Canaveral on November 26, 2011, at 15:02 UTC aboard the MSL spacecraft and landed on Aeolis Palus in Gale Crater on Mars on August 6, 2012, 05:17 UTC. The Bradbury Landing site was less than 2.4 km (1.5 mi) from the center of the rover's touchdown target after a 560 million km (350 million mi) journey. The rover's goals include an investigation of the Martian climate and geology; assessment of whether the selected field site inside Gale Crater has ever offered environmental conditions favorable for microbial life, including investigation of the role of water; and planetary habitability studies in preparation for human exploration.
In December 2012, Curiosity's two-year mission was extended indefinitely.