An execution is an activity that indicates the loading of a binary into the memory of a computer to run it as a separate process.
If two (or more) executions of the same binary are separated by less than a few minutes, the Engine aggregates them into a single execution. The duration of the aggregated execution spans from the start of the first execution to the end of the last execution. The cardinality of the aggregated execution equals to the number of different independent executions.
This mechanism naturally groups repeated or parallel executions of the same program, helping the Engine save space for data retention.