Why is this an issue?

The complexity of an expression is defined by the number of &&, || and condition ? ifTrue : ifFalse operators it contains.

A single expression’s complexity should not become too high to keep the code readable.

Noncompliant code example

With the default threshold value of 3:

if ((condition1 && condition2) || (condition3 && condition4)) && condition5
  ...
end

Compliant solution

if (myFirstCondition() || mySecondCondition()) && myLastCondition()
  ...
end