A conditional links a condition to a result.
Condition and result
If it rains, we stay home. The if-clause is the condition. The other clause is the result.
The four types
Zero — a general truth: If you heat ice, it melts.
First — a real future: If it rains, we will stay home.
Second — unreal now: If I had time, I would help.
Third — unreal past: If I had known, I would have helped.
If it rains, we stayed home. — mixed up
If it rains, we will stay home. — first, a real future