An SPC is one company with many compartments. Cayman and BVI company law provides that the assets of one segregated portfolio are available only to the creditors and investors of that portfolio, and cannot be used to meet the liabilities of another. The SPC holds the fund licence, the board and the service-provider appointments once, and each new portfolio launches under them.
For fund platforms this matters because a new fund does not need its own company, licence, bank accounts or provider contracts. The economics of the whole SPC are shared, while the legal separation between portfolios is statutory rather than contractual.