WebElement and WebDriver

WebDriver driver = new ChromeDriver();

WebElement u = driver.findElement(By.id("user"));

1. in first line, I am creating driver objct of class ChromeDriver which implements WebDriver inteface, is this understanding correct?

2. 2nd line -

findElement is a method on interface WebDriver. This method returns an object of interface 'WebElement', is this correct?

findElement method is present under both WebDriver and WebElement class, why?