A trade mark can be any sign which distinguishes the goods or services of one undertaking from those of others. It can be a word or a picture. It can be a shape of a container. It can be a colour or a combination of colours.
Registration grants a statutory monopoly to use of the mark.
You can use the registration to prevent others from using the same or similar mark on the same or similar goods or services. Owners of well known marks can even stop others from using their mark on totally different goods. Also, probably more important to the smaller trader, the first person to register a trade mark in good faith can use it to stop someone who started to use the same or similar name earlier but who didn't register it. The problem is that under the Trade Marks Act of 1994 it is the first applicant who is deemed entitled to any registration not necessarily the first user. Therefore, I cannot really advise anyone to use a trade mark on an unregistered basis because if someone else did get a later valid registration, that could be used to prevent further use of the unregistered mark.