When dressing comfort, it is very similar to Athleisure in terms of dressing for comfort rather than wearing anything tailored, for example. Casual is much broader as you can wear a lot more, such as heavy material shirts, and other clothing that isn't made for proactive wear.
Your personality can really be shown as casual is more personal and doesn't have any rules to follow to match the style. Whether you prefer a laid-back look, minimalist, or even the most vibrant colors you can find, you are wearing casual!
Check out these links to learn how to properly dress this style: