There are many Joomla templates that are based on different front-end frameworks. Since the customisation of third party extensions plays a large role in the process of website creation we have foreseen different themes to provide the correct component display in different templates.
Front-end frameworks provide styles unification and as a result all HTML elements that are created matching the standard of framework will be displayed in common style. For example: icons, forms, fields, links etc. To display elements in common style third party extensions try to add the support of frameworks on the template level.
NorrCompetition includes the following themes:
To decide what theme you will need to use you should know what framework is used in Joomla template on your website. For that you should read the description of the template on the template provider page or to examine the CSS/JS scripts in page source code.
In case your template uses framework that is not supported by NorrCompetition then select the default theme.
Note. Component themes include only layouts without any forced inclusion of frameworks. That keeps your website light and prevents the duplication of libraries and also gives great possibilities for integrators to choose between different front-end frameworks.
You can create a custom theme that will support needed layout/framework. Please read more in Template Overriding document.