According to Wikipedia a personal information manager includes one or more of the following features:
Bookmark manager - for storing web site URLs
Calendar - for managing appointments & daily agenda
Contacts - optional, since smartphones normally handle that
Email client - optional, since email clients are ubiquitous now
Forms - for items that require predefined template
Notes - for any kind of free-text information
Outliner - for drafting ideas & organizing hierarchical data items
Reminders - for appointments & to-dos
Task manager - for managing tasks and todo lists