Developers who know which component to select should do so. Platform is the type of computer the reporter was using when he or she noticed the bug. OS is the type of operating system the reporter was using when he or she noticed the bug. Priority indicates how imporant this bug is. Priority P1 is the highest priority and it is given to bugs that should be fixed as soon as possible.
Critical bugs prevent the usage of the product.
In contrast, Enhancement bug reports request new functionality in addition to what is currently working. Assigned To contains the email address of a developer who is assigned to fix this bug. By default, this field is filled in based on the component the bug is reported against. If a reporter knows that a particular developer should fix this bug, he or she can fill in that developer's email. Normally, this field is filled in after the bug has been seen by developers.