Magic is a helpful tool for writers that can allow for any abstract nonsense that comes to mind. Unfortunately, sci-fi creators don't usually get the chance to play with the mystic arts. Luckily, they do have advanced technology, and with a Techno Wizard at their disposal, anything becomes possible again.
The advancement of technology is the central element of science fiction. Plenty of stories are entirely built around the advent of some incredible new scientific marvel, while others feature plenty of fantastical inventions as background details. Plenty of sci-fi stories need at least one character who understands the future tech and knows how to use it to solve just about any problem.
The Techno Wizard is a character that can do anything and everything with technology. They're hyper-intelligent, competent beyond logical explanation, and resourceful above all else. They're usually not particularly good at anything other than the manipulation of electronic devices, but the varied uses of futuristic technology move them far from a one-trick pony. When a sci-fi writer needs someone to explain their concepts, the Techno Wizard will come in with a relevant string of concepts that may or may not stand up to real-world scrutiny. Typically, other characters will handle action and social interaction, while the Techno Wizard makes the impossible possible. The name is somewhat literal, as they often fill the same role an actual wizard would in a fantasy story.
The Techno Wizard is something of a character archetype that fits easily into a team of heroes. They'll usually fill the "smart one" role on the crew, and they have a few typical personality traits. They're usually hyper-fixated on their particular interest, often launching into ecstatic rambles whenever their favorite topic is brought up. They tend to be kind, but shy. In extreme cases, they feel more empathy for the machines they work with than the people they work alongside. They tend to be meek in physical stature, or at least not as ripped as the rest of the cast. When they rattle off their techno-babble, most audiences tune out. Soft science fiction is the typical home of the Techno Wizard. Hard sci-fi typically prefers to spread its knowledge around its cast and handle it more realistically. The Techno Wizard appears across all kinds of stories, but they're often a fan favorite in their own right.
Children's TV loves to make use of the Techno Wizard trope. Of course, the ur-example is probably Donatello, the smart one of the Teenage Mutant Ninja Turtles. He fits every metric with ease. In many ways, he built the mold and defines the terms for other characters to meet. Kim Possible had Wade, the tech genius who invented all of her cool gadgets. Danny Phantom had Tucker, the nerd who could move mountains with his early-2000s PDA. Chip 'n Dale: Rescue Rangers had Gadget Hackwrench, the beloved inventor who used assorted garbage to assemble nanomachines, among other absurd things. Several hit cartoons star a Techno Wizard. Dexter's Laboratory, Jimmy Neutron, Phineas and Ferb, and more classic series starred eponymous geniuses who solved all their problems through invention.
Perhaps the preeminent Techno Wizard is the Doctor from Doctor Who. The Doctor occupies the wizard archetype more effectively than most characters who actually cast spells from within a robe. The character probably owes more to Gandalf than he does to any science fiction classic. The Doctor doesn't have a lot of things that would be considered superpowers, he (or she) survives primarily on millennia of acquired knowledge. That endless breadth of information allows the Doctor to manipulate all manner of technology from across time and space in fantastical ways. Though the Doctor certainly owns some stellar tech, he's also proven that he can make just about anything work. On multiple occasions, the Doctor has picked up a modern smartphone and turned it into a piece of technology more advanced than anything we've seen on Earth. Though the character differs in many ways from the standard, he codifies the essential elements of the trope. The Doctor is the ultimate Techno Wizard, and he still sets the standard for those who follow in his footsteps.
The Techno Wizard serves several important functions in a science fiction narrative, and they're not even limited to that genre. Police procedurals like CSI: NY and Leverage make use of modern Techno Wizards. The hackers blurting out nonsense about firewalls and mainframes evolve into much more complex beings as technology evolves around them. When a writer needs to make the impossible possible in a realm without the slightest supernatural element, Techno Wizards have them covered. When they need someone to explain how the world works and what's going on, the Techno Wizard is the perfect mouthpiece. Though their existence could be purely functional, many Techno Wizards have gone on to be beloved characters.