You know what happens when you write long winded articles in your blog or post a verbose comment in a forum? Someone will come in and say “tl;dr”. Well, some Wikipedia articles leave me with the same feeling. Wikipedia writers and editors are so thorough that they like to cram all the information that they can accumulate into the articles. Although that makes Wikipedia a great place for researching on a subject, it’s unsuitable when you need quick information – something which is short and easy to understand.
Simple English Wikipedia is a version of the Wikipedia encyclopedia that was born in 2004 to cater to the special needs of students, children, or adults with learning difficulties or short attention span developed as a result of addiction to things such as Twitter. 
Articles in the Simple English Wikipedia use fewer words and easier grammar than the Ordinary English Wikipedia. Because of the simple language the Simple English Wikipedia helps people understand unfamiliar topics or complex ideas. The Simple English version tends to stick to commonly accepted facts and rarely tells you more than you want to know. For instance, compare these two different articles on “Special Theory of Relativity”.
Ordinary English Wikipedia article:
Special relativity (SR) (also known as the special theory of relativity or STR) is the physical theory of measurement in inertial frames of reference proposed in 1905 by Albert Einstein (after the considerable and independent contributions of Hendrik Lorentz, Henri Poincaré and others) in the paper "On the Electrodynamics of Moving Bodies". It generalizes Galileo's principle of relativity–that all uniform motion is relative, and that there is no absolute and well-defined state of rest (no privileged reference frames)–from mechanics to all the laws of physics, including …… *yawn*
The Simple English Wikipedia article on the other hand, begins matter-of-factly
Special relativity (or the special theory of relativity) was developed and explained by Albert Einstein in 1905 because he was unhappy with the explanations of electromagnetism in the physics of the time. Einstein thought these explanations did not agree with the principle of relativity…
The second article is definitely easier to comprehend.
Simple English Wikipedia is a good place to go if you need to answer questions coming from a fifth grader. Like say your kid wants to know why the Second World War took place. Simple Wikipedia will come to your rescue. However, not all Wikipedia articles have a simple English version. At the time of this writing, the Simple English Wikipedia had 58,145 articles, as opposed to more than 150,000 in the original Wikipedia.
Quick Tip: The quickest way to get to the simpler version of a Wikipedia article is to replace “en” in the URL “en.wikipedia.org” with “simple” to make it read “simple.wikipedia.org”. If however, a simpler version of that article is not present you will find yourself reading the original article (even though the URL says “simple”).