Licensing Options:

Non-exclusive:

The buyer pays a license fee for each time the image is used.
Another buyer can purchase the same image as well as use it under the same license.
Image details to be specified during purchase: Usage, media, image size, placement, region, industry, and duration.
The price will vary based on the required use.
 
Exclusive:

The buyer pays a license fee for each time the image is used.
The buyer receives exclusive usage of the image according to the terms of usage as specified.
Image details to be specified during purchase: Usage, media, image size, placement, region, industry, and duration.
Exclusive usage is generally preferred for high impact projects such as ads, promotions and campaigns during which you are guaranteed to be the only holder/user of the purchased image. 
The price of exclusive use is generally 15 to 30 % higher than Non-exclusive.
 
Copyright Purchase:
 
The buyer pays a one time purchase price for the specified image.
Ownership, rights, and copyright of specified image are transferred to the buyer upon purchase completion.
The original image, backup copies, and any versions of purchased image are deleted from my disks upon successful transfer of image. The buyer becomes responsible for creating backups upon receipt of image.
Copyright purchase pricing varies greatly according to the image.
Buyer retains image after completion of project for future use.