The eval command is a distributable streaming command, which means that it can run on the search peers in a distributed environment1. The search peers are the indexers that store the data and perform the initial steps of the search processing2. The eval command calculates an expression and puts the resulting value into a search results field1. In your search, you are using the eval command to create a new field called "responsible_team" based on the values in the "account" field.