It is generally considered that there are 6 types of informal reports. These are as follows:
- Information Reports
This usually follows the format of introduction, main body and conclusion. These reports are usually just data based, and used to stack necessary data e.g. Daily activity.
- Progress Reports
These are progress-based reports that satisfy questions in the vein of, 'is anything in addition needed to complete the activity?' or 'is everything running according to plan?'. It is essentially a troubleshoot checker.
- Recommendation Reports
These reports are largely oriented around analysis. This is the trouble shoot report, offering solutions to problems and evaluating pros and cons.
- Feasibility reports
How feasible is the project? These reports suggest whether it is likely to fail or succeed, and whether it's wise to invest (further) capital.
- Minutes of Meeting
This is a report that accounts for all details of the meetings, including date, time and discussions.
This is the final evaluation of the entire project, and aims to provide an overview of performance.
I hope this helps.