CSS stands for Cascading Style Sheets. Its a web language used mainly to make HTML easier to work with and enhance a lot on a page. Its meant to work with HTML, so if you don't know HTML you can't realy use CSS. There is a few things which are similar with the two, though really its not to much:

1. State properties.
2. You must end it.

Yea, not to many similarities, but now lets see the differences:

1. CSS effects the entire page or everything you specify, HTML effects a small area only inside the tags.
2. CSS starts with <Style type="text/css"> and ends with </Style>
3. When you want to change a property, lets say you want to make all bold text white you'd have to add: b{
   color:white;
   }
   

Now we see the differences and similarities. CSS is pretty easy, once you get the hang of it. It saves a lot of time cause you don't have to write the html tag t change color or something constantly or anything else and can write a couple lines of code effecting the entire page. Now you want to learn how to use this stuff yea?