What Is "the Crisis"?

everything keeps saying pre-crisis and post-crisis in dc comics, what is the crisis!?

by 1985, DC's multiverse had gotten out of had with like 8 versions every character. so in order to condense it to one single, simple universe they created the crisis on infinite worlds. i would suggest picking up the 12 issue maxi series as it is rather enjoyable. unfortunately, not to long after, they had to do a major house clearing again with the zero hour crossover, to much less success than the crisis.

everything precrisis happened before the maxiseries and everything postcrisis is post maxiseries.

This site http://www.io.com/~woodward/chroma/crisis.html pretty much explains it all.

a silly solution to a silly problem. they create a multiverse, realize it's too complicated and edit it out of existence with a super deluxe crossover mini-series where every page has a different character dying... then they create another multiverse, realize it's too complicated... yadda yadda yadda.