There is no classic order book with a buyer facing a seller. There is a pool: a pot holding two tokens, say ETH and USDC. Whoever wants to swap takes from one pile and puts into the other, and a formula, the AMM, recalculates the price automatically. The people who fill the pot are the LPs, and they earn a fee on every swap.

The pool and the AMM

That is the whole primitive. Uniswap made it famous, and every decentralized exchange since is a variation on it. Everything an LP earns and everything an LP risks follows from being the counterparty to every swap that crosses the pool.

Concentrated liquidity, and the real job of an LP

In early designs your money was spread from zero to infinity, so almost all of it sat unused. With concentrated liquidity (Uniswap v3 and everyone who copied it), you choose a price range: "I provide between $3,000 and $3,500 per ETH".

Narrow range: you earn far more fees, but the smallest move pushes you out of the market.
Wide range: you earn little, but you sleep at night.

The critical moment: out of range

What going out of range means

When the price leaves your band you are out of range. Two immediate consequences: you stop earning any fees at all, and your money has fully converted into just one of the two tokens, the less desirable one. Your capital sleeps and melts at the same time. And nobody tells you: not the DEX, not your wallet. It is a silent event that can run for weeks, which is exactly why out-of-range detection is one of the most measurable alerts Otomato sends.

Impermanent loss, explained without a formula

You put ETH and USDC in a pool. ETH doubles. All the way up, swappers came to take your ETH and leave you dollars. At the end you hold less ETH than you started with, and you earned less than if you had done nothing at all. That gap is impermanent loss. It is called impermanent because the gap closes if the price returns to its starting point. In practice, it rarely returns.

The real P&L of an LP is: fees earned + emissions received minus impermanent loss. If that total is negative, doing nothing would have paid better.

The working vocabulary

Rebalancing: moving your range after the price moved. The core gesture of the LP craft.
Automated vault: a bot that rebalances for you, for a cut of the gains. Convenient, and worth auditing: a badly tuned rebalancer on a small pool can bleed a position on every rotation.
Slippage: the gap between the price you expected and the one you got, because your own swap moves the price.
Aggregator: a service that splits your swap across pools for the best price. On a modern DEX, most volume arrives through aggregators and bots, not through the protocol's own website. A DEX is a liquidity layer, not a web page.
Arbitrage: bots that make a living correcting price gaps between venues. They cost you impermanent loss and pay you fees. They are your main customers.

Check yourself:You LP ETH/USDC between 3,000 and 3,500. ETH runs to 4,200. What do you hold, and what do you earn?(tap to reveal)

You hold only USDC: on the way up, the market bought all your ETH around 3,500. You are out of range, so you earn no fees at all. And you missed the entire 3,500 to 4,200 move on the ETH you used to hold. Until you rebalance, your capital sleeps in the wrong token.