The term "illiquid" is used to describe the most volatile and risky investments in the financial market. This term is particularly relevant to mutual funds, which tend to have rules preventing

Illiquid assets are those resources that cannot be sold without the owner losing a significant amount in their value. It will be a challenge for a person to sell them due to lack of an interested buyer

The only think you need to know about liquidity can be summed up in one sentence. Liquidity is never there when you need it. When there's a full on rout, there's no where to unload your position.