A recording studio is where music
or other sounds
or recorded media
The center of any recording studio is their mixing board, also called a mixing console when they get fancier. This is where the volumes of individual sounds can be adjusted, as well as details such as equalization and amount of effects are determined with switches, knobs, and faders. Small studios may have a 16-channel board while larger studios, especially movie production houses, may have a several hundred channel console. Often, to facilitate mixing, the consoles will have automation, where movements of the volume faders are recorded and played back each time the recorded song is played.
The other main part of the studio is the multitrack recorder. This may be an analog tape recorder (such as an OTARI or Scully), digital tape recorder (usually Tascam DA-88s or Alesis ADATs), or a hard disk based recording device (standalone or as a part of a computer). Each track on these tapes may have only one instrument recorded on it, necessitating many tracks for a large band (or a band with a big drum set).
Any studio which records music with non-electronic instruments will have at least one "live room." This is where the musicians perform. These rooms will often have lots of acoustical soundproofing and muffling, in order to get the cleanest possible sound into the recording.
An important aspect to a particular recording studio is their microphone cabinet. Good studios have a wide array of different types of microphones, and know how to properly use them with any instrument they may come across.
Studios also have some amount of outboard gear. This can be anything from compressors to reverb units to distortion pedals. Sounds can be routed through the mixer to these devices to effect the sound coming through.
Perhaps the most important part of any recording studio, though, is the recording engineer. She or he must be intimately acquainted with all of the equipment, but also must have a delicate musical ear to be able to bring subtle acoustic nuance through to the listener. A good engineer can make beautiful music in nearly any studio, but a mediocre engineer will only make mediocre recordings no matter the studio with which she or he is equipped.