In order to understand the meaning of this metric one needs to understand a concept of Bitcoin Days and Bitcoin Days Destroyed. Please read detailed description here.

`"Liveliness" = (sum_(i=1)^n "Bitcoin Days Destroyed"_i) / (sum_(i=1)^n "Bitcoin Days Created"_i)`
Liveliness is a sum of all Bitcoin Days ever destroyed divided by the sum of all Bitcoin Days ever created.
At every data point it takes into account the entirety of Bitcoin history up to that point and naturally is a very macro level metric.

Periods of steep Liveliness raises show intensive coin destruction going on in the market.
While periods of plateauing indicate dominant holding behaviour in the market and usually happens in bear markets / bearish phases.

The metric was introduced by Tamas Blummer in this article.