Conference calling: It involves a conversation between more than 2 people simultaneously. For example, consider this- There are 3 callers: A, B and C. When all the 3 callers are connected on one call simultaneously, then it is referred to as a conference call.
Call transferring: It involves transferring calls from one person to another by dialing an extension number. For example, consider this- There is one customer A and 2 agents X and Y. If customer A calls agent X, and agent X transfers the call to agent Y then, this entire process is referred to as a live call transfer.