Bollinger Bands: What are they?

There are many different views concerning technical analysis for cryptocurrency trading and investing. Along with those views, come a host of chart indicators, each with their own stated advantages. Each trader has their own bias on which indicators work for them.
One indicator sometimes referenced in the crypto space are the Bollinger Bands.
What Are They?
Bollinger Bands (also abbreviated to B.B.) are a charting indicator invented by financial analyst John Bollinger. They comprise three specif