This referendum moves 25k KSM (roughly 10%) of the Kusama Treasury from its account on the Relay Chain to its account on Asset Hub. It also sets the asset rate of KSM to 1 (since the conversion of KSM to KSM is unitary). Having an asset rate value is required to spend from the Treasury on Asset Hub.
This requires root privilege, but once the funds are on Asset Hub, it will allow normal operation with the Treasurer and XSpender tracks.
Having the funds on Asset Hub will enable new Treasury features like staged spends (detailed by @muharem on the forum). When this works successfully, I will propose the same thing on Polkadot, where we can take advantage of more features like USDC/T spends and funding sub-treasuries.