What is the need/use for enable annotation processing for Lombok?

Question

I am new to maven and was looking into using Lombok.
I added the following to my pom:

<dependency>
  <groupId>org.projectlombok</groupId>
  <artifactId>lombok</artifactId>
  <version>1.18.24</version>
</dependency> 

I also added the following class:

import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;

    @Data
    @NoArgsConstructor
    @AllArgsConstructor
    @Builder
    public class User {
        private String firstName;
        private String lastName;
        private String email;
    }

Now what is not clear to me is how from this class code is generated. I have tried an example with json to pojo conversion and for that to work I had to add a plugin to the build cycle.
But in this case with Lombok when I clicked on package and then checked under target/classes I found that the User.class has a bunch of code added based on the anotations.
But how exactly was that code added? I googled a bit and it seems that this code generation happens because of enabling annotation processing in the InteliJ preferences but when I checked my IDE that was not set. So how was the code generated?