How JSON is converted into Apex class in Salesforce?

You can create a wrapper with a list of objects like below and deserialize JSON to the wrapper.
Example:
Public class JSONtoApexClasses{
Public List<JSONtoApexClass> tickets {get; set;}
public class JSONtoApexClass{
public String SUMMARY;
public String CUSTOMERUSEREMAIL;
}
public static JSONtoApexClasses parse(String json) {
return (JSONtoApexClasses) System.JSON.deserialize(json, JSONtoApexClasses.class);
}
}