Some sample covers can be viewed at these links
4867 ages of Mad goodness is here.
Mad is a humor comic/magazine. It is known for satire and absurd humor. Some of the humor is topical and may depend for full appreciation on your being familiar with the thing being satirized, such as a movie or book. Mad is still published today, nearing issue 500. Personally I'm not too happy with the recent years of it's publication, but maybe that's because I'm approaching late youth and out of touch with things. These issues however, are from the glory days
EC Comics started it in the pre-comics code era. EC was known in those days especially for it's Horror titles and others that were not approved of by those who wanted to be censors. EC was devastated by the comics code. Their other titles did not survive the new climate in comics. Mad survived, the only EC title that was left in the end. Amusingly EC stands for "Educational Comics". They strayed rather far from that name, not least in Mad,
Mad was a a new kind of comics for them and quite original. It spawned imitators such as "Cracked" but I think it was always the best of it's kind. A traditional comic book at first, it changed formats in issue 24 and thereafter many might argue it's not really a comic. It became a magazine. It does however contain a great deal that is clearly comics in the standard sense, and I think the issues after the change can still be lumped in with comics for many purposes. Notably, the DCP comics group scans Mad today, so they seem to have voted my way.