What is lora and how do I use it on my existing model ?

What is lora and how do I use it on my existing model. Can anyone tell me what did it do and what to do after I download it ?

Simply put, a lora is a sub-model that is trained on specific objects/concepts/styles and is used on top of the main model to transform the image.

To use the lora, you must first download it to a folder like STABLE DIFFUSION\models\Lora, and then call it through the buttons in the interface.
Then it should appear in your prompt tab with something like <lora:lora-name:1>, where 1 is strength / intensity of lora, which you can adjust.