Have you ever noticed that when you use an all true bypass pedal board, or long lengths of guitar cable that your tone starts loosing some of the high frequencies, and sounds a bit muddier, or muffled? If you have then you need a buffer!
A buffer is simply a circuit that takes the output from you guitar, replicates it as closely as possible but outputs it as a low impedance signal. Now that may sound a strange thing to do, but what it means to you is that the signal between your guitar and amp will degrade less, which should mean that you hear a truer representation of your guitars natural sound.
A buffer isn't the right choice for everyone, especially those using certain fuzz pedals, but to some it has a similar effect to that feeling after you have been swimming and your ears are full of water, you know when it finally drains and you go "I can hear again! Everything is so clear and unmuffled!" Err...
Anyway the 072 is a dedicated buffer, best sat right at the beginning of your chain. It is TL072 op-amp based, which is similar to a certain buffer found in a pedal named after a mythological beast...