Customer Purchase Latency is a measurement of the delay between customer purchase events (orders). It's in the form of a time, usually a number of days. So a 30 day Customer Purchase Latency means 30 days pass between orders.
This is usually aggregated across all of your customers into Average Customer Purchase Latency.
Eric Davis
Analyze your customer behavior
A quick and automatic way to measure your customer behavior is with Repeat Customer Insights. It'll automatically import your Shopify data and run a number of analyses to highlight different customer behavior.