Conceptual Framework

I like this definition of a conceptual framework by Miles and Huberman (1994):

A conceptual framework explains, either graphically or in narrative form, the main things to be studied - the key factors, constructs or variables - and the presumed relationships among them. Frameworks can be rudimentary or elaborate theory-drive or commonsensical, descriptive or casual. (p. 18)

Reference
Miles, M. B., & Huberman, A. M. (1994). Qualitative data analysis (2 ed.). Thousand Oaks, CA: Sage.