Vesicles are used in cells to transport materials through out the cell like a semi truck. They go from one organelle to another and sometimes even outside of the cell. This process some times begins with proteins being transported by vesicles to the golgi apparatus where they are then moved again by vesicles to the cell membrane to export the materials. Vesicles can be created naturally by endocytosis, protein absorption, or created artificially and are then referred to as lipsomes. Vesicles are composed of phospholipid bilayers, sometimes more than one, and these fuse with other organelles, like some of the fore mentioned.
Structure
Vesicles have a structure similar to the structure of the cell membrane. They are composed of a lipid bilayer that moves around the cell to where ever the materials are needed. Sometimes the vesicles will transport materials to the outside of the cell and when they do this, they fuse themselves to the cell membrane and open towards the outside of the cell, and push its contents outside the cell.