I heard that tight clothing on woman is not permitted,
It shows the shape of the body.
Is this true? what does this mean practically?
The most comprehensive book on the subject is Rabbi E. Falk's 700 page "Sefer Oz Ve-hadar Levushah: Modesty, an Adornment for Life : Halachos and Attitudes Concerning Tznius of Dress & Conduct" which you can preview - and partially read - at Google Books.
He discusses the guidelines of tight clothing, and why it's an issue.
You can search the book for tight, to get some ideas.