A "id" is an attribute (properties used to provide additional information about an element) which identifies an element. A "id" can only be used oonce on a page. A "class" is an attribute that classifies an element. A class can be used multiple times on a page and you can put multiple class together with different attributes by adding a space in between each class name.
A style of css when the compuer reads the commands from the top to bottom and displays them one after another, selecting the bottomw ones with more permanence.
whatever is displayed in the element of parent tag when defined by css with a value. All of the elements now have the define value.
Being specific down to the element(s) you wish to change in html.