What is an animatic?
[an-uh-mat-ik]  / noun
1. a preliminary version of a film, produced by shooting successive sections of a storyboard and adding a soundtrack.
Most people don't know that almost every advert and feature film they sit and watch had an animatic made for it.
The animatic is a very important part of the journey from script to screen and yet you're unlikely to see or hear about it.
If the animatic isn't planned and executed well the whole job could be pulled by the client.
A brief history of animatics.
When I first starting working on animatics in 1999 we shot real paper art work on a rostrum camera. 
An illustrator would turn up in the morning with a big cardboard envelope of art work. We would normally be supplied with the background sheets and all the moving parts drawn separately on other sheets.  
Back then I was a trainee so it was my job to cut out all of the characters and moving parts with a scalpel.
because animatics normally have limited turnaround and financial constraints, they used to be intentionally simple. The skill came from getting the idea across with just camera moves, good editing and limited animation.
Each shot had to be laid out on the rostrum table and covered with cel to stop it blowing or moving mid take, it was very time consuming and you had to make sure everyone liked the shot before moving on to the next one.
Making changes wasn’t just a case of opening up the setup and re-rendering. It all had to be done again.     
Although the studio where I trained were already using macs running COSA (the very first version of After Effects) render times were very long so we only used them on shots that needed visual fx and tried to do as much under camera as possible.
It used to be that in order to make Animatics you needed a full spec studio. below is just some of the kit we needed.
Modern Animatics
The most popular types of animatic at the moment are the 2d and 3d animatic.
2d animatics are often drawn on a cintiq or wacom tablet direct into the computer and then coloured digitally.
The art work is still supplied in the same way as “the old days” but now the shots arrive as layered files with moving parts cut out and separated by the illustrator.
The advantages with the modern workflow is many animators are also skilled with the most used art programs, so if the client requires a change to the colour palette or longer sleeves etc, the animator will make the changes and minimise any delays in production.  
The modern 2d animatic can include quite sophisticated animation and particle fx. In fact most animatic studios use the same hardware and software that high end commercials and film studios use. The limit is set by budget and time constraints.

3d animatics use 3d models instead of drawings, a few years back these were all the rage and they were being requested regardless of the script.
The fact is some scripts work great as 3d and some scripts work better as 2d. 
Other types of research material that come under the banner of animatics are:
Photomatics: These are films made from photos of actors posed and shot on location or in a studio and then placed on to photographic or drawn backgrounds.
Stealomatics: These are films made from freeze frames or clips from movies, tv shows, magazines etc.
Mood films: normally the same as above and cut to music. More often than not these won't try to attempt to explain the narrative of the intended end script, just give the viewers a feel for how the end product will look.  
So, in short, the agency will spend some time and money on the animatic to make sure the ideas are working. They can then use this to work out any problems that might come up when filming the real ad.