What is it when the author paints a picture in the reader's mind using descriptive details and the senses?

Oh, dude, that's like when the author goes all Picasso on you and starts throwing around Words like they're paintbrushes, creating a masterpiece in your brain. It's called "imagery," and it's basically when they make you feel like you're right there in the story, smelling the roses and hearing the birds chirping. It's like Virtual Reality, but with Words.