The acronyms ATH and ATL denote the expressions 'all time high' and 'all time low', respectively. ATH indicates the maximum price attained by a given cryptocurrency throughout its history. Contrarily, ATL refers to the minimum price ever registered by a cryptocurrency. 

The ATH/ATL metric is employed as one of the numerous considerations in the process of trading digital assets. The ATL approach entails purchasing assets when prices are low. ATH however, is an approach of refraining from acquiring assets that have already reached their ATH. ATL/ATH helps investors and traders make decisions to acquire or divest digital assets.