Try Matt Finch's
Quick Primer for Old School Gaming for a better summary of the intent.
Note that this "movement" is more than a decade old, and has had plenty of time to turn on itself, schism into factions, and re-define itself. There are as many versions as there are writers, many of them contradictory.
Note, also, that as a gamer who lived through the era (started playing in 1976), I sometimes find my recollections at odds with the features that OSR advocates ascribe to it.