The game has a light ruleset that encourages roleplaying. Most conflicts are resolved with a percentage roll and a consulting table with the GM having a lot of flexibility due to rules being mostly just guidelines.
MSH has a quick and easy character generation process. Characters are created by rolling for origin, ability scores, powers, talents and deciding on a name. It usually takes less than 10 minutes and offers an impressive variety in characters created.
Karma is a resource used for character advancement and increasing chances in a conflict. It's gained by performing actions that a moral hero would perform.
Karam system is used for 2 things in the game - advancing the character (getting new powers, abilities and raising ability scores) and improving character's rolls. Since most players tend to focus on advancing the character, the secondary function of the karma system is often wasted potential.
Characters are built by expending Character Points on abilities, skills and advantages, and by choosing powers and complications. To balance the characters, the game imposes certain restrictions on what's possible based on game's chosen power level.
M&M includes a variety of archetypes that players can base their characters off of. There are 15 archetypes to choose from. For example, there's a speedster archetype for Flash-like characters and shapeshifter archetype for Mystique-like characters, etc.
In 2019 a "Basic Hero's Handbook" has been made for newbies to the game. It is a stripped down version of the full rules meant as an introduction to the system.
Because characters like Superman and characters like Catman are balanced by the game to be comparable in strength it may be difficult to suspend your disbelief.
Once you get the two charts down this system runs pretty quick. Allows a wide range of styles to play. Blood of Heroes also adds a few clean up to the rules. Writeups.org has a ton of extra heroes as well as others outside DC.
You can use your various Traits (Powers, Resistances, Aptitudes) in various ways. You can attack and defend with any trait. Each trait can only be used once by round barring advantage or special power (like armor).
While the game has an option for a point based character creation system, there's a random roll system that often produces exciting, unexpected results.