Multi effects units combine all the common effects and some uncommon ones into one box usually with a range of switches allowing you for example to create different patches allowing you to go from a clean sound with chorus straight into a high gain lead patch with delay with the press of a button. Infinite sounds in a compact package, the swiss army knife of guitar effects.
Reverb pedals modify the signal in such a way that you can replicate playing in different sonic spaces. Delay pedals allow you to repeat your sound at pre-determined intervals after you've played it. Both effects whether used independently or together can add warmth and depth to your tone. Reverb and delay pedals are collectively known as time-based effects and are typically positioned at the end of your signal chain.
