If you're under the age of 30, you've probably never seen a turntable outside of a movie, and if you're under the age of 20, you may have never seen one in a movie. Turntables are used to play old vinyl LP's and records, and they work by dragging a needle lightly through a spiral groove on a record, going from the outer edge to the inner zone.
This needle would be used to make an oscillating electrical current, which was used to drive speakers and make a sound. A lot of the audio technologies we take for granted (High Fidelity, stereo sound) were first pioneered in turntables.
Turntables were supplanted by CD players on the market in the 1990s. It was in the late '80s that sales of new titles on CD supplanted those on vinyl LP's, and most record labels quickly switched formats to the CD, which allowed customers to select which track they wanted more readily, were smaller, cheaper to produce, and produced a more pristine sound.
What's changed since then is audiophile appreciation of the turntable. The analog reproduction mechanism makes a sound that's more 'alive' or 'warm' than a digital file, and lots of music from the '50s through early '80s never got re-encoded to digital formats. The current range of turntables mostly applies to nostalgia buffs, who want to either listen to music that isn't available on CD or MP3, or who want to experience the music the way it was experienced back in the days of vinyl.
Many turntables sold these days have modern enhancements - for example, digital signal processor chips in the turntable itself can be used to tune the sound as it comes through the needle, and is used to give needles sensitivity that they never had back in the days when spinning disks were king. Others try to remain true to their original manufacturing stats - if you want to experience a Rolling Stones LP from the '70s, you need a turntable build like those from the 1970s, forgoing many of the technological innovations that have come since then.
Still others, like turntables in the '80s, are multi-platform devices, able to play back CDs, LP's, cassette tapes and more. Quite a few, following the lead from several devices in the '90s, will transcribe an MP3 copy of the LP file. Modern high-end conversion files, in an attempt to give the benefits of vinyl in a format that can be played on an iPod, use amazingly high bitrate transcription modes to catch all the subtle undertones of the richer vinyl sound.
For true nostalgia buffs, nothing beats the warmth of vinyl, and some of the more retro designs for turntables come from Rek-O-Kut and Stanton, which, depending on their models, try to get the exact feel (including remanufacturing older parts) to get the exact same sound as a Vintage Turntable.
