If you’ve used CSS before, you’re probably familiar with the distinction between ID and class selectors. The ID selector selects items by ID, such as #element1, whereas the class selector selects elements by CSS class. Use the ID selector when you just need to pick one element, and the class selector when you need to select a collection of elements with the same CSS class. There’s a strong possibility that you’ll be asked to develop code utilizing ID and class selectors during your interview. Another distinction between ID and class selectors is that the former utilizes the “#” character while the latter uses the “.” character.