Product Backlog Item (PBI)
Items in the Product Backlog are called Product Backlog Items (PBIs) in Scrum.
A PBI may represent any need such as: Business Functionality, Technical Enhancement, Change request, Defect, Support ticket, etc.
Scrum does not prescribe any specific way to write PBIs. Many teams find lightly written User Stories (a practice from XP Engineering Practices) to be a useful practice.
Suggested Reading:
Also see: User Story, Spike, Technical Debt, Product Backlog Refinement