BOLD:CSS is important because it allows web designers, developer, bloggers, and so forth to make our websites unique and attractive. CSS gives us the opportunity to play with a page layout, adjust colors and fonts, add effects to images, etc.
While in the past it was possible to add style via HTML or more simpler CSS, CSS3 has really expanded and allows for more creativity.
Ultimately, it makes our lives easier. CSS allows us to separate the presentation from the structure (HTML) into different files.