How can a person be "functionally illiterate"?

Functional illiteracy does not mean that a person can not read or write but what they comprehend or how well they express themselves. The generally used example is that someone who is functionally.illiterate is unable to read and comprehend an entire newspaper and is not able to properly fill out a job application. If you observe people around you, you will probably note that there are many who can read something, but if you were to ask them something about what they read, they really have no idea what was there or maybe just one or two points. They can read and write well enough to get by (function) but not well enough to improve where they are in life. If you look at this site, you will find many questions and answers that appear to have been written by a 3rd grader with misspelled words, improper punctuation, and grammatically incorrect. Some answers are incomplete, irrelevant or touch on only a part of the question asked. They may be hurried or careless ------ or functionally illiterate. Hope this helps.