What's the difference between first and second conditional? When can you use them both? When it's the right time to use this one or this one?
Well, the short answer: first conditional, we use that conditional for realistic situations. When something is likely to happen, it has a strong possibility of really happening.
So, a real situation. For example, in London, it rains a lot.
So, if we talk about the possibility of rain today, then I would use a first conditional because that possibility is strong. It's very likely that it will rain.
So, I use a first conditional in this form. If it rains today, I'll stay at home.
The form "if" with a present verb: rains. "Rains" because "it", and the result of that condition is in the future, "I will" or "I'm going to", both are okay.
Again, I use this because in London. . . Nah. . . always rains.
And the second conditional, we use that to talk about imaginary or hypothetical situations. Maybe that situation is not likely to happen. Not a good possibility of it happening. Or maybe it's impossible.
For example, if I imagine that superman comes here now. That's not realistic. It's not possible.
So, I would use a second conditional sentence. "If Superman came here now" — that sounds a bit strange — we're using a past verb with "now".