Name four principal parts found in reports and proposal

The four principal, and most common, parts found in reports and proposal are:

Summary, introduction, discussion of findings, conclusions and/or recommendations.

Explanation:

Summary: is really a condensation of the most important points. It begins most short on informal reports, but the summary for a formal report is put on a separate page with a heading.  

Introduction: depending on the focus, it may have subsections. It can include several or all of these topics: purpose, background, scope and method.

Discussions of findings: it discusses the details of the report or proposal, the facts on which you have based your conclusions or recommendations. It explains what conclusions do you made by searching and thinking about the theme.

Conclusions and/or recommendations: There are differences between them. Whereas conclusions are the inferences you have made from your findings, the recommendations are your suggestions about what actions to take, in face of those conclusions.