The Rubik's Revenge (aka the Master Cube) has a 4x4x4 cube layout, making it harder to solve than the original Rubik's Cube. Aside from the 8 familiar corner pieces, this puzzle features twice as many edge pieces and 4 center pieces on each of its faces (compared to only 1 on the Rubik's Cube). This puzzle was released in 1982 and was actually not invented by professor Rubik himself but by Péter Sebestény, who later sold the rights to his invention to the Rubik's Brand (owned at the time by Ideal Toy Corporation, and today by Spin Master).
The most common way to solve the Rubik's Revenge is called the "Reduction Method". As implied by its name, this method focuses on solving the 2x2 center pieces and 2x1 edge pieces first. Then treating them as single pieces, and thus "reducing" the problem by making the puzzle equivalent to a regular 3x3x3 Rubik's Cube, which can then be solved using the normal 3x3x3 solving methods (along with two parity cases that require separate algorithms). An interesting concept to keep in mind while solving this puzzle is that even-order puzzles don't have any fixed facets. That means that the center pieces not only need to be color-matched but also positioned on the right face. This stands in contrast to the odd-order puzzles in which the center-most piece is fixed in position and can be used to infer the color of the face it is placed on.
This puzzle has quite a few more moving parts than the original Rubik's Cube. Therefore, it has many more possible permutations. The number of possible permutations of the Rubik's Revenge is over 7.4x1045. It is an official WCA puzzle, and the current world record for solving it is 16.79 seconds, set by Max Park from the USA at the Bay Area Speedcubin' 29 PM 2022 competition.