Events that happen as you go along can be used to "leak" more information to the reader. For example, say you're telling the adventures of a character named Fred, and you have not yet said anything to the reader about his physical appearance. You can draw that picture step by step:
(1) Fred walks through a doorway, and has to lower his head--you've shown the reader that Fred is tall.
(2) Fred needs to hurry to overtake someone on the street, and his knees ache from the long, quick strides--you've shown that he has arthritic knees, and either is old or has suffered stress to his joints.
(3) Fred is thinking about something and scratches his head--but you specify that he scratches his head "just above his receding hairline," showing that he's partly bald.
(4) Fred changes clothes at home, and finds that his favorite pair of pants has become too tight around the waist--you've shown that he needs to lose weight.
These steps are an alternative to just flat-out saying, "Fred was a tall, aging, balding man with a pot belly." Not that you _can't_ just say it flat-out if you prefer; style is a matter of taste and of the intended effect. But hey, can you blame me if I wanted to display a little of the kind of writing-style discussion that occurs in the "Marketplace of Technique" thread? (Uh oh, I think they ARE blaming me, better take off!)