What "does first come first serve" mean?
First come first serve is an English idiom
An Idiom is a recurrent sentence that we can use in multiple situations with the same meaning. It is a good way of showing that we know the language, and they are used frequently (but not exclusively) in oral language.
It means that no queue /waiting list is expected/allowed.
It can be used in a non regulated setting, where many people want to buy/achieve something and it will be bought /achieved following the order of arrival.
Examples
We didn't get the tickets' for Taylor Swift's concert as it was first come first serve. When we logged into the platform everything was sold out.
I went to the butcher's to get some minced meat but there was none of it left. First come first serve! Next week I will go earlier.
Some English expressions connote different meaning than the literal definition of the actual words used.
Others are somewhat upfront. Once you know their meaning, it is easy to understand their derivation.
However, some can still be difficult to decode without some help since it is mainly a shortcut for saying something.
Just like with "first come, first served".
The thought is there but grammatically speaking, the sentence is incomplete.
What does it mean?
"First come, first served" means that you will be served base from the order of your arrival.
This expression is usually used in stores or restaurants.
Some establishments have these exact words on their signage.
First come first serve is the right expression.
it's commonly used in restaurant settings. People will be dealt with in the order in which they arrive or apply. so the restaurant is not taking any reservations.
First come first serve is the right expression.
First Come First Served is a quotation.
This means that those who have lined up first will be given the first opportunity to be served.
When you book an appointment to a doctor. Those who have appointments will be served first than those who just walked in.
This is used to indicate that people will be dealt with strictly in order in which they arrive or apply.