Teaser poster VS theatrical poster

A teaser poster is released in advance to promote the film early and make people aware of its existence. Then when the proper poster and trailer is released, the audience is already hyped for it. They are simplistic, in the way that they only have a basic image and design, with very little information about the film. The mysterious element of the teaser makes the audience wonder what the plot is about, who the characters are and what themes are included.

Here is the teaser poster for the film: World War Z

This picture doesn't even have an image, the main graphics is just the title with 'Z' being the largest letter. Brad Pitt's name is at the top, to attract fans and let the audience know that this will be a huge film, since this A list star is in it.
All we can tell about the film so far is that there is en epic war, judging by its title. This is already exciting because we want to see all the devastation caused by whatever has caused this disaster. That's the second most intriguing feature; why is it called the 'Z' war and who is the enemy? What part does Brad Pitt play in this? We can assume that he is a hero, since he is the protagonist. But who does he have to fight? What is at stake here?
It is a sophisticated teaser, which doesn't need to display all its graphic content in order to gain attention. The star's name, intriguing title and release date are enough to show to get attention.

Here is the real poster for the film.
A predicted, we can now see the devastating state of the world. Judging from the guns, helicopters, smoke and fire; we can expect lots of thrilling action, explosions and crashes in the film. There is still lots of mystery in this poster, since we can't see the enemy and we don't know what exactly Brad Pitt's character is doing there and what he's looking at. The 'invisible' enemy makes the premise of the film more terrifying. It must be a super powerful force to throw the world into chaos. The producers are purposely not showing it to save the big reveal for the film; which is a very effective way to generates hype.
The design of the title and positioning of the star's name, are elements that have been carried on to this poster. They are almost identical, apart from the colour and sharpness of the 'Z' as well as the how visible Pitt's name is against the background. It is important to carry on some of the features, so that the audience will associate the earlier hype with this film. It builds a brand identity.
However, those features are less prominent on this poster, since they now rely mostly on the main image to capture the audience's eye.
The real poster has more information (like the specific release date) because it is closer to the film's release, so the audience needs to be aware of when/where it's coming out, if they want to go and watch the film.