How exactly to categorize Bitcoin is a matter of controversy. Is it a type of currency, a store of value, a payment network or an asset class? Fortunately, it's easier to define what Bitcoin actually is. It's software. Don't be fooled by stock images of shiny coins emblazoned with modified Thai baht symbols. Bitcoin is a purely digital phenomenon, a set of protocols and processes. It also is the most successful of hundreds of attempts to create virtual money through the use of cryptography, the science of making and breaking codes. Bitcoin has inspired hundreds of imitators, but it remains the largest cryptocurrency by market capitalization, a distinction it has held throughout its decade-plus history. (A general note: according to the Bitcoin Foundation, the word "Bitcoin" is capitalized when it refers to the cryptocurrency as an entity, and it is given as "bitcoin" when it refers to a quantity of the currency or the units themselves. Bitcoin is als