Conditional
1. Open conditional
An open conditional leaves it open whether its condition is satisfied.
If he loves her, he will change. If he loved her, he changed.
2. Remote conditional
2.1. Remoteness. Modal remoteness is expressed through the preterite. The matrix clause also takes a preterite form to mark modal remoteness. To distinguish the sentence from an open conditional, this preterite form is carried by an auxiliary verb, usually would, the preterite form of will. In many cases, tense is determined by context (Even a finite clause may not explicitly indicate tense).
If he loved her, he would change. If you came tomorrow, we could talk together.
2.2. Remoteness + perfect. The perfect auxiliary have marks the perfect, while its preterite form also marks modal remoteness. The matrix clause likewise uses the perfect auxiliary have to mark the perfect. When tense is supplied by the surrounding context, the event time (\(ET\)) of the sentence is interpreted as earlier than the time indicated by that tense:
If she had gone to bed, it would have been better.
2.3. Degree of remoteness. The degree of remoteness may vary with context: a remote conditional is not always counterfactual.
If you wanted, we could leave now.