Traditionally, alternative assets (like real estate and some types of private credit) have been slower to buy or sell than public market assets (like equities and bonds). Often, this is because they are not traded on a screen with daily liquidity. Likewise, the market may be smaller with fewer eligible buyers and sellers, or the transaction may have to be privately arranged.
Liquid alternatives, on the other hand, can be bought or sold more frequently. Some fund structures (like ETFs) can help achieve greater liquidity. For example, Invesco offers a broad range of commodity ETFs with daily access.