“I can think of enough examples of people who started out small and are now the proud owners of a trademark that is famous around the world. Just think of all those DJs who had their names registered six or seven years ago. Back then no-one thought that the names of famous DJs would become so valuable. Their interests are now protected all over the world.”
The legal definition of a trademark is very broad: trademarks are all signs which distinguish a company's goods (products) or services. This broad definition with the reference to all signs means that more distinguishing signs can be protected as trademarks than you perhaps may have thought at first. The following are a few examples:
1. Word marks: The name by which a product or service is on the market.In practice, 99% of registered trademarks belong to categories 1 (word marks) or 2 (device marks).
However, it is also true that not all signs can be trademarks. If you file a sign that cannot be a trademark, the BOIP is obliged to refuse its registration. More information is available here.