Templates are user-created pre-designed "profiles" that you can apply to yours to quickly change its appearance.
To apply a template, simply navigate to the "Templates" section in the dashboard sidebar, browse through the available templates, and select the one you like. Once you apply a template, you can further customize it to suit your preferences.
Some templates are available for free, while others are exclusive to Premium users. What makes a template Premium is the options used in it. If a template uses any Premium-only options, it will be marked as Premium.