Trade marks are used in commerce for distinguishing your goods and services from others.
A trade mark can be formed from a word(s), slogan, logo, sound, stylization, smell, colour, effectively anything that can identify and distinguish your goods or services from those of others.
Trade marks can be a Registered right (signified by the R in a circle ®) or an unregistered trademark - signified by “TM”.
Unregistered trade marks rights exist under the Fair Trading Act and common law. An unregistered trade mark is limited by the reputation and goodwill and under only has effect where that mark has established reputation, e.g. a Nelson business using an unregistered trademark may not be known outside Nelson and so another business may be able to setup in Auckland with the same trademark without infringing. In contrast, a registered trademark gives the owner the right to stop unauthorised use of that trademark anywhere in NZ.
Registered trademarks are also far easier to enforce than unregistered trademarks.
A trademark is registered with respect to particular goods or services that the trademark will be used for, e.g. Cadbury has registered trademarks for chocolate but not cars.