Pictures from noise
Most image generators use a technique called Diffusion model: The technique behind most image and video generators: start from random noise and clean it up step by step until a picture appears.. During training, the model sees millions of pictures with their descriptions. Each one is covered with random speckles, like the static on an old television, and the model learns to clean the static away.
To make a new picture, it starts from pure static and cleans it up step by step, guided by your description. Each step makes the image a little clearer, like a photo slowly coming into focus, until it matches what you asked for. Because the starting static is random, the same request gives a different picture each time.
Some newer generators work differently, building the picture piece by piece the way a chatbot writes. For you the experience is the same: describe what you want, look at the result and ask for changes.
Video that holds together
A video is a series of still pictures shown quickly, dozens every second. Making one good frame is the easy part. The hard part is consistency: the same face and shirt from start to finish, objects that don't melt or vanish, and movement that obeys physics.
Most video models handle this by working on the whole clip at once, cleaning up all the frames together so they agree with each other. That takes far more computing power than a single picture, which is why video is slower to make and costs more. Some video models also create matching sound, from footsteps to dialogue.
Voices and music
Text-to-speech: Turns written text into a natural-sounding voice. turns written text into a spoken voice. Modern voices pause, stress words and show emotion in natural ways, and some services can copy a voice from a short recording. Speech-to-text: Turns spoken audio into written text. Also called transcription or ASR. does the reverse, turning speech into written words for captions, meeting notes and voice typing.
Some assistants now handle speech directly, so you can talk to them, hear the answer and interrupt as you would with a person. Music generators can write and perform a whole song, vocals included, from a short description of the style and mood you want.
Things to watch out for
These tools make things up. A picture of a real street can show shops that aren't there, text in an image can come out garbled, and a transcript can mishear a name or number. If a detail matters, check it.
Be careful with real people. Realistic images, video or voices of someone made without their permission can hurt them, mislead others and, in many countries, break the law. Most services block or limit this, and many add hidden watermarks or labels to show that something was made by AI.
Before you use generated work in an advert, a product or anything you sell, read the service's terms. Some only allow commercial use on paid plans, open models have their own licences, and the copyright rules for AI-made work are still unsettled in many countries.