A combined mark is a type of mark that includes two different elements - one is text, and the other one is graphics. The text is usually in a stylized form to match the brand identity. Moreover, the mark includes some graphical elements, such as an icon or a special drawing unique to the brand. For example, the golden arches of the McDonald's logo with the text McDonald's underneath would be considered a combined mark.
If a combined mark is registered, all the dominant elements of the mark have implicit protection. That means that if a competitor uses one specific element of a combined mark in separation, the protection granted to this element depends on its uniqueness.
For example, a business might be able to register a combined mark containing its name and a graphical element, but in case a competitor uses a similar brand name, the question would become if the competitor's brand name infringes on the text element of the combined mark alone - and here, the text element in isolation might not be considered distinctive enough on its own.