Where does the problem will be reported?
Launchpad in general and specifically: to the package the crash occurred on. By the way: if this specific crash is already known you will get a notice regarding that.
What would happen if we cancel it?
No report will be filed.
What could be the possible Reasons of such occurrence?
Bug in a program. Faulty hardware. Unsupported features in hardware.
Is there any Log/History files to view the sent Report?
The program apport (Ubuntu specific) stores crashes in /var/crash
. (See https://wiki.ubuntu.com/Apport and this on U&L).
How to know that the problem was solved or being solved?
Track down the bugreport number and visit Launchpad.
Ways to report it manually, if we found?
Sure you can manually report a bug on Launchpad BUT you will need to get all the information added to a bug report otherwise it will be marked as "incomplete".