I report on my personal behalf
Submit a report as a private individual. On personal behalf can also be used for submitting a report anonymously.

By reporting on personal behalf you are submitting a single but new report every time you use this function. You will not have the possibility to submit updates for the same report, for instance by using the same off-line form again. Such updates will be considered equivalent to submitting a new report. Reporting on personal behalf will not provide an E5Y file (what's this?).
I report on behalf of my organisation
Submit a report for an organisation, or when their services are contracted by an organisation. If your organisation runs its own internal reporting system then you are encouraged to report via that system and not via this site.

Reporting for an organisation does not allow to report anonymously; your credentials will be asked for during confirmation of the information entered. If foreseen, you may receive via e-mail an E5Y file (what's this?) that you can use for posting updates to the same report submitted via this site.