A crane is a lifting machine, that can be used both to lift and lower materials and to move them horizontally.
Cranes are used to large amounts of heavy materials that would not normally be humanly possible.
Cranes are normally used in the transport secter for moving freight, and in the construction industry for moving manufacturing materials and equipment.

As you may of heard in the news lately there has been a massive story involving the malfunction of a crane, as it plowed in to a block of flats. Cranes can be vulnerable in high winds as on the ground it may be a nice day but 30m in the air it could be a very different story.
The health and safety officer dealing with this case are trying to do everything humaly possible to remove the crane from the building.