ID: An ID is an attribute that is used to uniquely identify an element on a web page. An ID can be used to identify one element, or multiple elements if the same ID is used for each element.
Example:
This is the introduction paragraph.
Class: A class is an attribute that is used to group elements on a web page. A class can be used to identify one element, or multiple elements if the same class is used for each element.
Example:
This is the introduction paragraph.