A descriptive text is a text that wants you to picture what they are describing.
A novel might want you to imagine the characters and see them in your mind.
A travel book will want you to see the country it is describing.
Descriptive texts usually:
make use of adjectives and adverbs
use comparisons to help picture it - something is like something
employ your five senses - how it feels, smells, looks, sounds and tastes
Examples:
The morning air was crisp and sharp as Sean walked down the road.
The pavement was slippery and cold beneath his feet like a slimy wet fish.
To learn more about words to help you describe people, places and things look at the Skillswise Describing words (adjectives) module.