What does the title 'Modern OPS' means?

'Modern OPS' stands for 'Modern Warfare 2' and 'Black OPS' (Modern + OPS = Modern OPS)

What is Call of Duty Modern Warfare 2?

Call of Duty: Modern Warfare 2 is a first-person shooter video game developed by Infinity Ward and published by Activision for the Xbox 360 and PlayStation 3 video game consoles and the Microsoft Windows operating system. Officially announced on February 11, 2009, the game was released worldwide on November 10, 2009. It is the sixth installment of the Call of Duty series and the direct sequel to Call of Duty 4: Modern Warfare, continuing along the same storyline. It was released in conjunction with two other Call of Duty games: Call of Duty: Modern Warfare: Mobilized for the Nintendo DS, and Call of Duty: Modern Warfare: Reflex, a port of Call of Duty 4 adapted by Treyarch for the Wii console. In addition, a comic book series based on one of the game's characters was also produced, entitled Modern Warfare 2: Ghost.

Modern Warfare 2 has received very positive reviews from various gaming websites, attaining a 94% aggregate score on Metacritic, with praise stemming primarily from its in-depth multiplayer component. Upon its release, the game sold approximately 4.7 million copies worldwide in 24 hours. On June 15, 2010, Activision confirmed that the game had sold over 20 million copies worldwide and it is the best-selling game of all time in the UK , and the second best-selling game of all time in the U.S.

What is Call of Duty Black OPS?

Call of Duty: Black Ops is a first-person shooter video game developed by Treyarch, published by Activision and released worldwide on November 9, 2010 for Microsoft Windows, Xbox 360, PlayStation 3, Wii, and Nintendo DS (separate version developed by n-Space) consoles. Announced on April 30, 2010, the game is the seventh installment of the Call of Duty series, and the first to be set in the Cold War. It is the third in the series to be developed by Treyarch, and is a sequel to the developer's Call of Duty: World at War.

Within 24 hours of going on sale, the game sold more than 7 million copies, 5.6 million in the U.S. and 1.4 million in the U.K., breaking the record set by its predecessor Modern Warfare 2 by some 2.5 million copies. A subtitled version was released in Japan on November 18, 2010. A Japanese-dubbed version will be released on December 16, 2010.