A Beginer's Guide To Guitar Effects Pedals

We're going to try to give a quick look at the major types of guitar effects pedals. Here in part 1 we'll cover the basics.
We know that there are a Metal Distortion Pedals offering insight to this topic, but its been our experience that they're written by engineers, not musicians... they read like microwave manuals rather than a helpful resource... Anyway... off we go.
Boost
I can't really milk more than a few lines out of this topic. It's pretty cut and dry- a boost pedal will give your signal a volume boost - or cut, depending on how you've got it set. Most boost pedals act as a master volume control allowing you a pretty wide range of use.
Why do I need a boost pedal? To bring your guitar volume up over the rest of the band during a solo, to drive your amp harder by feeding it a hotter signal, to have a set volume change at the press of a button.
Overdrive
When most guitarists talk about overdrive, they are referring to the smooth 'distortion' produced by their tube Tremolo Pedals driven to the point of breaking up. Overdrive pedals are designed to either replicate this tone (with limited success) or drive a tube amp into overdrive, creating those screaming tubes beyond what they normally would be able to do without wall shaking volume.
Why do I need an overdrive pedal? Overdrive pedals can be used as a boost pedal- so you get those inherent benefits, you'll get some added girth to your tone from the distortion created by the pedal. Most overdrive pedals have tone control giving you wider tone shaping possibilities.
Distortion
Based on our above definition of overdrive, distortion is where overdrive leaves off. In the rock guitar world think Van Halen and beyond for a clear example of distorted guitar tone. Distortion pedals often emulate high gain amps that create thick walls of sound small tube amps are not capable of creating. If you're fortunate enough to have a large Marshall, Mesa Boogie, Diezel or other monster amplifier to create your distortion you might not need a distortion pedal. But for the rest of us mere mortals, distortion pedals are crucial to modern guitar tone.
Why do I need a distortion pedal? You want to be relevant don't you? Even with large amps, like those Multi-effects Pedals above, distortion pedals play a key role in modern music. They offer flexibility that boosts and overdrives can not rival.
Fuzz
God bless Ike Turner and the Kinks. Both acts achieved their landmark tones by using abused speaker cabinets. Ike dropped his on the street walking in to Sun Records to record Rocket 88, the Kinks cut their speakers with knives or so the legends have it. No matter how they got it, their tone changed the world. Some call it distortion, some call it fuzz, however, seeing the progression from these damaged speakers to the fuzz boxes built to emulate those tones, I think its safest to call what Turner and Davies created/stumbled upon was fuzz.
Why do I need a fuzz pedal? Ya like Hendrix, don't ya? In all honesty, the fuzz pedal is seeing resurgence in popular music these days. Bands like Nine Inch Nails, Marilyn Manson, Muse and the White Stripes rely heavily on classic designs on recent releases.
Compressor
The job of a compressor is to deliver an even volume output. It makes the soft parts louder, and the loud parts softer. Current country music guitar tone is driven by the use of compression.
Why do you need a compressor? Improved sustain, increased clarity during low volume playing.
Modulation
Flanger
The earliest "flanger" effects were produced in the studio by playing 2 tape decks, both playing the same sounds, while an engineer would slow down or speed up the playback of one of the dupe signals. This is how you could produce wooshing jet streams. The edge of the old school tape reels is called the flange.
Why do I need a flanger? A flanger will offer a new color to your tonal palette. You can live with out one, but you'll never get some of the nuance coloring of the Van Halen's, Pink Floyd's, or Rush's of the world.
Phase shifter
The phase shifter bridges the gap between Flanger and Chorus. Early phasers were meant to recreate the spinning speaker of a Leslie. Phase shifting's over use can be heard all over the first few Van Halen albums.
Why do I need a phase shifter? See Flangers answer.
Chorus
Chorus pedals split your signal in 2, modulates one of them by slowing it down and detuning it, then mixes it back in with the original signal. The effect is supposed to sound like several guitarists playing the same thing at the same time, resulting in a wide swelling sound, but I don't hear it. You do get a thicker more lush tone, but it doesn't sound like a chorus of players to me.
Why do I need a chorus? Because Andy Summers uses one, and Paul Raven says so... that should be good enough.
Tremolo
As a kid, did you ever play with the volume knob on the TV or the radio manically turning it up and down? Yeah? Well you were a tremolo effect.
Why do I need a tremolo pedal? 6 words for ya: The Smiths 'How Soon Is Now'
Delay
A delay pedal creates a copy of an incoming signal and slightly time-delays its replay. You can use it to create a "slap back" (single repetition) or an echo (multiple repetitions) effect. Who amongst us can't appreciate The Edges use of digital and analog delay throughout U2s career?
Why do I need a delay pedal? See Flangers answer.
Wah
A variable band-pass frequency filter... Screw all that- you know what a wah wah is... its porn music! It's Hendrix! It's Hammett. It's Wylde. It's Slash.