Twin Peaks is one of those ineffably sublime and absurd things which description only serves to describe less. It's a task for better wordsmiths, but I'll try.
Some *spoilers* to follow:
This show was born a decade or two early for television. It's an amalgam of cheese, melodrama, Dadaist humor, symbolism, classic Lynchian weirdness, and more. It is, in ways, both a parody of soap operas and a supernatural interpretation of one. If you don't get it, you don't get it. (Part of the joke is that, sometimes, there is nothing to "get".) If you do "get it", you'll feel that this was a show made for you. Of special note is the wonderful musical score by Angelo Badalamenti.
Don't look for any plans or myth arc here; Peaks was written without a plan, and it shows. Characters work more on magic and intuition than sense. The town of Twin Peaks is quirky, small-town with a seedy side, Tim Burton on a paranoid drug trip. You will get no explanations other than what's already there (or what's found in the viewers' minds). The quality of episodes varies as well. When it's good, it's very, very good; when Peaks is bad it's time to turn off the screen. It is also an example of one of the worst cases of executive meddling in television.
The first season is without a doubt the better part of the series. The second season, due to network pressures and an increasingly tuned-out audience, devolved into incomprehensibility. In other words, writers went full "artist" on the viewers. *Spoiler alert* Solving the central mystery of the show took out its heart. At the very first episode, Laura Palmer, unwrapped like a wilted blue rose, set the tone. Putting her to rest, so to speak, left the writers without a beat to follow. This is where the executive meddling came in.
Peaks stands as an icon, an aberration, a warning, an inspiration. Boundaries were pushed in terms of what television could do. But it also showed what could not be done. Push the audience *too* far and they won't come back. Transcendent in its bizarreness, Peaks has had a lasting impact on television. Its fingerprints are smudged all over the X-Files and LOST, to name a few shows. It was the epitome of a flamboyant failure.