Trade marks can be words, words in fancy fonts, pictures, logos, shapes, even smells. 

A trade mark need not be registered and even if it is not, in the UK you can still put the letters TM after it, to denote that you intend it to be considered a trade mark.

TM has no legal meaning however.

If your trade mark is not registered you will need to take someone to court and prove that you have goodwill in the trade mark and that another person was profiting through misrepresentation from users being confused by the use of that goodwill.

A registered trade mark provides you with the ability to simply claim infringement of your trade mark if someone else uses it or similar in relation to the goods or services (or similar) for which you have registered the trade mark.  Where there is a likelihood of confusion.