A conditional clause ties the assertion or action to another state of affairs. In, idhā and law all express conditional relations, but they differ in expected occurrence and temporal coloring.
«إن جاء زيد أكرمته»
If Zayd comes, I shall honor him.
«إذا جاء زيد أكرمته»
When Zayd comes, I shall honor him.
«لو جاء زيد لأكرمته»
Had Zayd come, I would have honored him.
These are explanatory contrasts rather than quotations from the source. The first leaves the event conditional, the second treats it as anticipated, and the third readily supports an unreal or counterfactual supposition. Context governs precise interpretation.