The first conditional has the present simple after 'if', then the future simple in the main clause:
if + present simple, ... will + infinitive
It's used to talk about things which might happen in the future.
Of course, we can't know what will happen in the future, but this describes possible things, which could easily come true.
If it rains, I won't go to the park.
If I study today, I'll go to the party tonight.
If I have enough money, I'll buy some new shoes.
She'll be late if the train is delayed.
She'll miss the bus if she doesn't leave soon.
If I see her, I'll tell her.
First vs. Zero Conditional
The first conditional describes a particular situation,
The zero conditional describes what happens in general.
Compare these two sentences:
If you sit in the sun, you get burned --> natural consequence of sunbathing (zero conditional)
If you sit in the sun, you'll get burned --> talking about today (first conditional)