My teacher told me that descriptive languages were used to describe things, and the example he gave was this: He is in a red cloth, he has blond hair, etc. And he said informative languages were used to inform people something, and the corresponding example was this: He was born in New York, he left the US in 1970 for his study in London. But I still can't discriminate them quite well. The examples here are both trying to describe something and inform something.
The lines between descriptive and informative language are not always clear, but roughly:
- Descriptive language is text that might help you recognize something; and
- Informative language is text that might help you understand something.
If you had to pick somebody up at the airport, and you'd never met them before, think about what kind of data you might like to be given: what they look like, or maybe how they behave ("he always heads straight for the nearest espresso bar, so you might be able to find him there").
Although probably not very useful in airport pickups, the way something sounds, tastes, smells, or feels is also descriptive.
On the other hand, explaining that the man you are picking up has a pair of 3-month-old twins is an informative statement. It might explain his espresso habit, but won't help you to recognize him. Informative statements help you to answer the "why" and "how" questions.