You are a company ...
...and your assistant is off for holiday, sick or on maternity leave ?
...and your company structure doesn't allow you to hire a secretary ?
...and you don't need a full time secretary, even not half time, or your budget doesn't allow you to hire an assistant ?
...and you wish to have more time available for your activities and not to spend too much time on office applications or administrative jobs ?
You are an individual ...
...and you need a report, a thesis, a paper, a memorandum in the briefest delay ?
...and you are not customed with administration or office applications, and you need help ?