The poster hasn’t got a clue of how venn diagrams work i guess. He/She just saw some here on graphjam and wanted to try that too. Well, here’s how it works:
http://en.wikipedia.org/wiki/Venn_diagrams

The term “mental retardation” is a diagnostic term designed to capture and standardize a group of disconnected categories of mental functioning such as “idiot”, “imbecile”, and “moron” derived from early IQ tests, which acquired pejorative connotations in popular discourse over time. The term “mental retardation” has itself now acquired some pejorative and shameful connotations over the last few decades due to the use of “retarded” as an insult. This may in turn have contributed to its replacement with expressions such as “mentally challenged” or “intellectual disability”. While “developmental disability” may be considered to subsume other disorders (see below), “developmental disability” or “developmental delay” (for people under age 18), are generally considered more acceptable terms than “mental retardation” among members of the disability community.