1. WEP session key
The WEP key that is generated for unicast traffic per user per session when using EAP it is a dynamic key
2. WEP broadcast key rotation
A method to rotate between the 4 static keys used for broadcast traffic to mimise the chance of someone cracking them
3. Transmission key.
in what context are you sure you dont mean unicast key ?? If so the WEP key used to encrypt unicast traffic can be either a static key or a session key