RACI is an acronym for:
Responsible–The person or people who actually complete the task and are responsible for implementation or action. Responsibility can be shared.
Accountable–The person or people who manage those responsible for the completion of the task. Typically only one person has this assignment per task.
Consulted–The person or people whose opinions are sought.
Informed–The person or people who are kept up-to-date on progress.
In addition to RACI, Supported By relationships can be used to describe how equipment or other resources play a role in supporting a process.