It defines something happening in a point or a period.
(See the full diagram)
It defines the concept of a person or an organization making an offer, basically proposing a resource or a future service in return for money.
It defines the concept of a person or an organization accepting an offer; then it becomes a purchase. This one can be preceded by a negociation occuring during a certain period.
It defines the change of possession or location without the change of ownership. It is usually a physical change of location.
It defines the change of ownership without the change of possession.
It defines a movement which does not affect any other accounting component. Typically the allocation of money on a balance sheet for tax optimization.