Impermanent loss only affects liquidity pools (through e.g. Spookyswap, Spiritswap etc) where there is more than one token locked in the pool. In simple terms, impermanent loss is the difference between holding tokens in the liquidity pool and holding them separately. It occurs when the price of tokens inside a liquidity pool diverge in any direction. The more prices diverge from each other, the greater the impermanent loss. It is referred to as impermanent because it would only materialise, i.e. become permanent loss vs the "buy and hold" strategy, once you break up the liquidity pool. If the price of the tokens in the pool return to the exact price as when you created the liquidity pool, the loss is neutralised. Your share of trading fees earned within a liquidity pool can offset impermanent loss, sometimes more than compensating for the impermanent loss, but this is not guaranteed.