>= has the expression evaluate to true for 'greater than or equal to'.
e is Entitye.expected_aum >= 10000000
Let's say that e, the entity in the case where this expression is used, is a small financial advisory firm in Lyon. The expression evaluates to 'true' if the firm, after a record breaking year all around, is expected to have ten million or more in assets under management.
This could trigger the need for extra documents to be included, if your organization treats corporate clients with ten million or more in assets under management differently than smaller firms. You might, for example, want to offer this client some extra services.
By attaching the this condition to the documents offering those extra services, you make sure they are offered each time the expression
e.expected_aum >= 10000000 is true.