Super Mario Maker was announced during Nintendo's digital event at E3 2014 on June 10, 2014 as simply Mario Maker. It was scheduled for release on the September 11th, 2015 for the Nintendo Wii U and coincides with the 30th Anniversary of the release of Super Mario Bros. for the Nintendo Entertainment System.
Super Mario Maker allows the user to create custom Mario levels. The game includes Super Mario Bros., Super Mario Bros. 3, Super Mario World, and New Super Mario Bros. U settings, and the user interface is deliberately reminiscent of the GUI from the Super Nintendo classic, Mario Paint, including the random appearance of flies on the screen that the player can swat and the use of a dog and a robot to represent the undo and save functions, respectively.
Though stages allow for a limited total width, they can be designed to force Mario to move both right and left. There also appears to be new power-ups not included in any previous Mario titles, including Luigi Mushrooms, which make Mario much taller and skinnier, and Mystery Mushrooms, which give Mario one of a variety of costumes based on other Nintendo characters.
The player can freely switch between edit and play mode at any time, allowing the player to play-test stages in progress. Most elements of a stage's layout can be edited, including the placement of pits and their width, pipe placement and height, question mark blocks and other floating blocks, moving platforms, coins, and enemies. Items can be freely arranged in ways that would not be seen in a real Mario game, such as by stacking a Goomba, a Koopa Troopa, and a Piranha Plant on top of each other. Players can also include a variety of extra sound effects in their levels, including ones they record themselves, though unfortunately, to prevent potentially exposing children to obscene language or noises, these recorded sound effects are not included when levels are shared online. These sound effects can be triggered by things such as enemies performing an attack, objects emerging from pipes, or even simply walking Mario over an invisible trigger.
Mario Maker supports the sharing of levels online as well a ranking system for the most popular levels. The game also includes a 100 Mario Challenge mode, wherein players must complete 16 randomly selected user levels with only 100 lives at their disposal, and a harder variant known as 10 Mario Challenge, where the player only has 10 lives to clear 8 premade courses.
A special "30th Anniversary 8-bit Mario" amiibo was released alongside the game in Classic colors faithful to the original Super Mario Bros. sprite and Modern colors which are more in line with Mario's current appearance. The amiibo itself is much larger than the standard figures and, appropriately, when used with the game will allow the player to add a Mega Mushroom to their course, causing Mario (or an enemy it's been applied to) to grow much bigger than normal.
Super Mario Maker supports over 75 other amiibo figures, using them to unlock various costumes based on the appropriate character for use in the game which can be donned by using a Mystery Mushroom power up. However, these costumes can only be used in the original Super Mario Bros. tileset. These costumes (as well as many others not tied to amiibo) can also be unlocked on their own without the use of the amiibo figures by completing various challenges.
Info from GiantBomb