The Settlement.Org website provides an overview of working for an employment or temp agency.

Whereas private ‘employment agencies’ act as employers and supply their employees to other organizations that need temporary help, they should not be confused with ‘employment services, which are government or non-profit organizations that help individuals plan, train for, and obtain ‘permanent’ employment.

Temp agencies place their employees in a wide variety of roles and environments, from offices to factories and from clerical staff to production line operators.

Newcomers and their sponsors should be aware of reports that not all temp agencies place their employees in good work environments. See for example, these media reports:

For a discussion of employee rights in a temp agency, see this article of the website, in English, and as a translated version, in Arabic.