Most of the text we read is expository. Articles in magazines, news stories and nonpersuasive speeches are examples. Anything that explains or defines a concept or process is "exposing" it to the reader and would fit under this category. Often, these texts are accompanied by pictures or charts to give further explanation.
It's important to grasp the main idea at work in an expository paper. What is the primary concept that the writer is trying to get across? How can the reader access and understand that main idea as efficiently as possible? While the headline can sometimes make this a very simple process, at other times, particularly if you're working your way through a government report, the main point can be difficult to find.
A series of directions comprises the whole of a functional text. This can be a 20-page manual about assembling and using your steam vacuum cleaner or the care tag on your new blouse. The purpose is to break down a process into its steps so the user can carry out the process correctly. While this may seem simplistic at times, just about every set of instructions on a product was written because a person had an accident.
It's important to follow the steps in order and to carry them out thoroughly. It is easier to do this for a curling iron -- as long as you stay out of the shower -- than it is for a cement mixer, because mixing cement is a much more complex process. The basic process of reading a functional text, however, remains the same.