Conditions optionally apply additional filters to control which issues will be impacted by Action(s) that follow.
There are three types of conditions :
JQL - Issues are filtered using start Jira Query Language
Compare Numeric values - Compare values in two fields that contain numeric values.
Compare Date values - Compare two fields that have date values.
The last two comparisons are faster in comparison to JQL. JQL is more comprehensive in filtering. In most cases it is not the optimal way to filter issues.