Reverb and delay are two of the most important and commonly used effects for guitarists. Reverb effects add space to the sound buy simulating the size of a room. Delay effects provide echo in a desired time and amount, and can incorporate other effects as well. In general there are two types of reverb and delay: analog and digital. Analog effects actually pass the signal through various circuits, whereas modern digital effects only simulate the analog sounds, often with more precision. The best reverb or delay pedal for you can depend on a number of factors: price (from cheap to boutique), size, and intended use