iOS Developer Certificates and Provisioning Profiles explained
CERTIFICATES VS PROVISIONING PROFILES
Certificates are used to identify a developer. The use a private key which must be distributed with the certificate.
Provisioning profiles are used identify an app. Provisioning profiles must be associated with a valid certificate.
TYPES OF CERTIFICATES
DEVELOPER VS DISTRIBUTION
There exists Developer certificates and Distribution certificates (and corresponding provisioning profiles). Developer certificates are used for running the app on devices using development. Distribution certificates are used to distribute the app to more than one user, e.g. for testing.
Certificates expire after 3 years for an enterprise developer account. They can also be revoked. A limited number of Certificates can be issued by a Developer.
Provisioning Profiles expire after one year or when the associated certificate expires or is no longer valid.
If the certificate/provisioning profiles expire or are invalid then users will no longer be able to run apps that have been signed with these. You must distribute a new version of your app that is signed with a new certificate and provisioning profiles.
OTHER CERTIFICATES
PUSH NOTIFICATION CERTIFICATE If this expires you can no longer send push notifications to your app.
APP STORE DISTRIBUTION CERTIFICATE If this certificate expires and your Apple Developer Program membership is valid, your existing apps on the App Store will not be affected. However, you will no longer be able to submit new apps or updates to the App Store.
APPLE WORLDWIDE DEVELOPER RELATIONS CERTIFICATION INTERMEDIATE CERTIFICATE The Apple Worldwide Developer Relations Certificate Authority issues certificates used by developers for signing third party apps and Safari Extensions, and for using Apple Wallet and Apple Push Notification services. Apple have issued a renewed certificate that must be included when signing all new Apple Wallet Passes, Apple Push Notifications, and Safari Extensions starting February 14, 2016.
RENEWAL
When a certificate expires an email will be sent to the Apple Developer account.
Renewal of the certificates and provisioning profiles happens via the Apple Developer Portal.