Name of the explanatory chapter in a cumulative dissertation how do you usually call the chapter of a cumulative dissertation (PhD thesis) that describes the research? A cumulative dissertation basically has two part: One part includes (published) research papers and the other part is an explanatory chapter that motivates the research and summarizes the it. 

So basically I thought of the following:
'Background chapter'
'Frame chapter' (that would be the direct translation of the German term

I'd apprciate every comment. Thanks in advance. 

Thanks for the current answer. Are there any other suggestions. I'd be happy to hear any comment on that.
Some places, such as Heidelberg, simply call it a "Summary". Others indicate that the Summary must place the papers in their "Scientific Context". I would favor the latter. But a specific university might provide specific guidance on this, as might an advisor.