Both are used to style the elements of HTML in CSS but there are some differences between them which are mentioned in the image: For a better understanding we can have an example let's see:- here HTML code <p class="paragraph">This is a paragraph.</p> <p class="paragraph">This is another paragraph.</p> <h1 id="header">This is the header.</h1> <div id="main-content">This is the main content area.</div> here CSS code .paragraph { font-size: 16px; line-height: 24px; } #header { font-size: 32px; font-weight: bold; } #main-content { width: 80%; margin: 0 auto; }