Amplifiers are useful for making your sound bigger, however, you will need one for an electric guitar. Amplifiers are usually pretty easy to match, if you have an acoustic-electric get an acoustic amp, bass guitar get a bass amp, electric get an electric guitar amp.
There is another type of amplifier called a P.A., which means a personal address system. these are the large speakers you usually see at the front of a concert or in front of someone making a speech. This is useful for getting your whole band heard.
Effect pedals go between the instrument and the amp, and change the sound coming out. the loud gritty sound commonly associated with rock is called distortion, which would use a distortion, overdrive, or fuzz pedal to get that sound. The list of different effects is long.
If you want some further help deciding what's best, check out our Buying guides.
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