It's a way to cut just the components/styles/themes/patterns out from a model and apply them into other models.
So if I have a Disney characters checkpoint, but I really like this MakeGiantEyes checkpoint, if I can get it down to a MakeGiantEyes LoRA, I can apply that on top of my Disney Characters model which is already a custom trained set. It definitely does not always work, but when it does it's like magic. At a practical level, it's a model-modifier.
... It took me a minute to get those because I had to sort through a LOT things that would probably get me banned here. If anyone wanted to know nationalities were using SD more... It's Asians, hands down, all day long, and I think that's interesting.
EDIT: And if you were wondering what a Textual Inversion is vs a LoRA... Don't ask me! They're both model modifiers, but as I understand it, textual inversions are good for faces (which is why most of those are people, and they are kilobytes in size), and LoRAs aren't as good for faces specifically but better for themes.
TI exmaples (I couldn't use any of the million women... there are almost none that would be appropriate to post. Even though civitai does a good job of removing the nsfw posts of real people even with cloths on some are just still too much... Thirst is driving AI now)
https://civitai.com/models/11039/ian-mckellen
or
https://civitai.com/models/8060/seu-madruga
