A theme is a personalized design of a website often including its layout. Changing your theme, changes the view of how your website looks on the front-end. Usually CMS platforms have both free and commercial versions. These themes are categorized as per their functions like
Free themes are found in theme providers and they are free of charge, but sometimes the features are more limited than that of the commercial ones. Let us take the free WordPress themes as an example. These themes are found on the following link – https://wordpress.org/themes/, you can find and install them as per your business profile or needs.
On the contrary, for the commercial themes, you must pay. WordPress commercial themes are found on the following link – https://wordpress.org/themes/commercial/.