Though the PMBOK doesn't explain it, these would be your proprietary tools (i.e. Microsoft Project for #2) or a Web-based application within your corporation's Project Management Office for #1. #3 could be your human resource management tool that tracks how many hours your employees work so they are paid correctly. There isn't a one size fits all. If it helps you clarify further, think about #1 being a largest database of all the projects going on, #2 is the software to help you manage a single project, and #3 helps you with scheduling resources for use within a project.
