Trademark registration protects all unique elements of the trademark. This means that should you opt for protecting your logo with a trademark, both visual and text elements of such a trademark are implicitly protected assuming that they display a sufficient level of distinctiveness.
It is probably the best to illustrate this complexity with real-world examples. On the one hand, the logo of Ryanair takes the form of stylised text with a small visual element. A single trademark application containing the logo protects the small visual element, the text 'Ryanair' as well as the whole combination of the two. The underlying reason can be found in the very definition of a trademark and its purpose which is to distinguish the products/services of one company from others, preventing customer confusion in any form. As a result, if the text element contained within the logo trademark is dominant and distinctive enough, an argument can be made that should a different competitor attempt to brand own products/services with this brand name, consumer confusion would follow.
On the other hand, trademarks displaying low distinctiveness, i.e. they are rather descriptive of the business offering, are highly unlikely to achieve a strong level of protection for the brand name itself. Examples can be made of numerous businesses with rather generic names, such as Napoli Pizza or London Furniture. In both of these cases, the brand name alone does not meet the criterion of distinctiveness for the trademark to be successfully registered. In these cases, a logo trademark may be recommended to be registered as it is the combination of the rather generic brand name with unique visual elements that allow the brand to distinguish its products/services on the market. While a trademark for the logo can be successfully registered in these instances, the level of protection extended to the brand name itself is very limited.
More information about the differences between registering the text and logo trademarks, as well as practical guidance regarding the choice of the most suitable option can be found in our Trademark Academy.