Identity keystore - For others to access WebLogic using https
This will be used to store the server certificate(private key/digital certificate pairs). When the client contacts server the digital certificate presented in this keystore will be sent. You may also need to store root and intermediate certificates in truststore.
Trust Keystore - For WebLogic to access others (consumes webservices) using https
This will contain all the certificates for the trusted partners(ie partners/clients). When server connects with the partner it will use this key store.