An informative text is a text that wants to advise or tell you about something.

A newspaper article might give you information about a health issue like giving up smoking.
A website might give you information about a movie, band or something that you are interested in.
A handout from school might be advising you about what your child will be doing during the next term.

Informative texts usually:

avoid repetition
contain facts
give information in a clear way - introducing the subject and then developing it

Examples:
Make a plan to help you try and give up smoking. Plan the date you'll give up, how you'll try to deal with temptations and a list of the reasons why you are giving up to keep motivated.