Risk Transfer simply involves transferring "only" risk to another person for a price. For example, the downside risk of stock can be transferred by purchasing a call option. In this way, the buyer of call option transfers its risk to the writer of the call option. Another example is insurance, wherein, the buyer transfers its risk to an insurance company.
Risk Sharing is an entirely different concept. It involves sharing (dividing) common risk with two or more person. I think, "partnership" is the most common practice of risk sharing. Banks also use this practice to lend a big amount to individual large size corporation.
