To put it simply, the certificate is the installation license. With it, you can sign the software you want to install, and the signed software can be installed on the mobile phone

S60 Chapter The third version has made major improvements in security, and has stricter regulations on third-party software installed and run in the system. Certain operations related to mobile phone software and hardware security/personal information security and other aspects have been specially restricted (for example, automatic startup when the phone is turned on is one of the restricted functions). Applications must obtain a "signature" to implement these "specially restricted" functions. In other words, someone must be responsible for the safety of this operation! Programs without any signature cannot be installed and run.