Here are the complete details:
ChromeOptions options = new ChromeOptions();
This creates an object by the name options of ChromeOptions Class.
Map<String, Object> prefs = new HashMap<String, Object>();
Here you have create a new Map object by the name prefs where the Key and Value fields accepts String and Object type of data and casted it to HashMap.
prefs.put("credentials_enable_service", false);
prefs.put("profile.password_manager_enabled", false);
prefs.put("profile.default_content_setting_values.notifications", 2);
In these three lines you have configured the pref-names within the prefs object.
options.setExperimentalOption("prefs", prefs);
Finally in this line you are using the setExperimentalOption method to set these experimental options (ChromeDriver options not yet exposed through the ChromeOptions API) within the optionsobject.
Now you can use this options object of ChromeOptions Class to initialize the WebDriver and Web Client as follows :
WebDriver driver = new ChromeDriver(options);