Any writing or drawing an image on any property without permission is called Graffiti. Street Art on the other hand is more elaborate than Graffiti and is usually done with the required permission of the owner to beautify the dull spaces.
While some people find it offensive, for others it is inspirational and a thing of beauty. Some street art get lost as it is ephemeral in nature but some always remains to inspire people like Werner Herzog,
who obtained special permission to shoot inside the Chauvet Caves of South France. He made a film about the world’s oldest pictorial creations, preserved for over 20,000 years, and called it Caves of Forgotten Dreams (2010).
The City of Melbourne acknowledges that public spaces provide a gallery for artists and has approved permits for street arts.
Legal Street art contributes not only for beatification of some parts of the city, it also encourages tourism into the city.
Walk down Hosier Lane in Melbourne to understand this and of being right in the middle of an art gallery. No wonder Melbourne is one of the World’s great Street Art Capitals.