The Infinity Stones are perhaps the most important artifacts in the MCU - more powerful than Thor's hammer, more versatile than Captain America's shield, and more destructive than Surtur's crown. Understandably for a mainstream product, the MCU movies don't spend much time explaining the intricacies of how the stones work, but even those details they do share tend to be at odds with how Marvel has depicted the stones in their comics.
In both the comics and movies, the individual stones give their users control over the primordial forces of the universe: time, space, reality, power, mind, and soul. In the MCU's Guardians of the Galaxy, Taneleer Tivan, aka the Collector, explains that the stones are remnants of six singularities that existed prior to the beginning of the universe. This origin is similar to the Marvel Comics explanation of the stones, but it's then that things diverge. Tivan explains that the stones can only be brandished by beings of extraordinary strength, telling the story of a group who were able to share the power of one stone momentarily before being destroyed by its power.
It's because of this that the MCU stones have to be used via some kind of intermediary device - the MCU's Time Stone is wielded through the Eye of Agamotto, for example, while Loki utilizes the Mind Stone through his Chitauri scepter. Once combined, even the Infinity Gauntlet can't negate the huge physical toll of using all the MCU stones at once, severely injuring the Hulk and ultimately killing Tony Stark in the Marvel movies.
These items have little relation to the stones in the comics, possessing their own unique powers, and in fact, the comics stones can be used safely by even the least powerful characters. The lead-up to 2018's Infinity Wars comics storyline showed characters like Black Widow and even Kingpin underling Turk Barrett hold and use their stones with no ill effects. There have actually been multiple sets of Infinity Stones (also known as Infinity Gems) in the Marvel Comics universe. The 'original' set was destroyed in Jonathan Hickman's New Avengers #3, when Captain America used them to prevent a cross-dimensional 'incursion' event, but new stones were created in the aftermath of 2015's Secret Wars event, in which the universe was secretly reborn in a new (but similar) form.
These stones worked by new rules, with each powered by the mastery of a primordial force characterized by another stone. For example, mastery of the Power Stone depended on the user's personal mastery of the mind, while the Mind Stone was powered by the user's mastery of the soul. This meant that, individually, the stones were only as powerful as their wielder's specific skillset, though together they still formed a positive feedback loop that would grant the user infinite power.
This 'circuit' approach is less essential in the aftermath of 2018's Infinity Wars, in which cosmic hero Adam Warlock sent the stones out into the universe to bond with individuals of their own choice. Currently, the stones exist in deep synthesis with individuals like Hector Bautista (aka Overtime) and Ripley Ryan (aka Star), creating some of the most powerful individuals in the world of Marvel Comics.
Ultimately, the Infinity Stones of the MCU are far more inherently deadly than their equivalents in Marvel Comics. This makes sense for their use as objects of ultimate power in the movies, where in the comics they exist in a larger ecosystem of incredibly powerful artifacts.