Think of a market maker as a used car dealer. Alice has a car that she wants to sell today and Bob wants to buy a car, but he won't be ready to until next week. The dealer will buy Alice's car today and hold it until Bob wants to buy next week (for a profit of course). Thus the dealer is making a market for Alicia to sell her car, and for Bob to buy one, without the two having to having to meet in time or space.

Market makers perform a similar function on illiquid stocks, where there may be more sellers than buyers at one moment but more buyers Jan sellers the next.

Speculators are simpler. They're the guy who buys Telsa roadsters because he thinks they will be a collectible soon.