To a genealogist of most levels, looks like a pretty easy question, no?
Actually, it is an easy question, but as with questions of this nature [Read: pretty ambiguous question.], I received a lot of related-but-not-quite-the-same answers. [And some were just plain funny.] Makes sense if you think about it. We're all different. And? It could depend on how you plan to use the chart or how you actually have used one in the past.
Take a look at just some of the answers [Help me give them a BIG thank you for particpating by clicking the links below the images for their Twitter Home Page or their Blog Home Page. Well, after you read my post. ;) ]
@ArchivalBiz - Also check out Laura's blog, The Last Leaf on This Branch.
@patmcast - Also check out Pat's blog, Peter's Blog.
"A pedigree chart is a diagram that shows the occurrence and appearance or phenotypes of a particular gene or organism and its ancestors from one generation to the next..." 
And yet another definition ~ this time from The Source: A Guidebook to American Genealogy, edited by Loretto Dennis Szucs and Sandra Hargreaves Luebking [Read: the best definition & I'm not surprised]:
"Pedigree charts provide an overview of generations or lines of descent. Pedigree charts are 'works in progress' where missing entries show areas in which further research is needed." 
And this definition - in fact, the second sentence of this last definition - is what is critical to understanding what a pedigree chart really is or, rather, how it can be used to accomplish research tasks.
But what form does it take? What does it look like? In 2012, it can look like a piece of paper with a chart quickly sketched out, it can look like a white board with the chart quickly sketched out, it can look like a computer screen with your genealogy software producing the diagram from your entered data, it can look like a pedigree chart print out from your genealogy database software, it can look like a tablet with the diagram on its screen, it can look like a smartphone in your hand with a diagram on its screen, or it can look like a mind map. [Although, I don't think at times my mind's map isn't nearly as organized as that app would lead one to believe.]
It's what a researcher uses to create their action plan for research tasks.
So. What specific form it's in [or should I say, "what platform it's on"?] doesn't really matter when you're researching so long as you use it to figure out what you already know and to figure out what you need to know. And this is sometimes hard for some of us to remember to do because we often times get caught up in searching online. [And searching and searching and searching.]
In the midst of all that online searching [which can be a good thing in moderation], are you remembering to check your pedigree chart? When was the last time you looked at your pedigree chart? What do you still need to find out?
 Pedigree chart. (2012, June 16). In Wikipedia, The Free Encyclopedia. Retrieved 20:28, October 17, 2012, from http://en.wikipedia.org/w/index.php?title=Pedigree_chart&oldid=497849248
 Szucs, Loretto Dennis and Sandra Hargreaves Luebking, "Record Your Findings," in The Source: A Guidebook to American Genealogy, Loretto Dennis Szucs and Sandra Hargreaves Luebking, editors (Provo: Ancestry, a division of MyFamily.com, 2006), 20.