The word pool has several meanings:

1. A body of still water, either naturally occurring or human-made. A swimming pool is built for recreation, while a tide pool forms naturally when ocean water gets trapped in rocks along the shore. After a rainstorm, you might see pools of water collected in low spots on the playground. The phrase pool of light describes a bright area surrounded by darkness, like the circle of light from a flashlight beam.
2. To combine resources with others for a common purpose. When your family pools its money to buy something expensive, everyone contributes what they can. Students might pool their candy after trick-or-treating to share and trade. A carpool works this way too: families pool their transportation, taking turns driving each other's kids to school.
3. The game of pool (also called pocket billiards), played on a felt-covered table where players use a stick called a cue to strike balls into pockets at the corners and sides. The most common version uses fifteen colored balls and one white cue ball. Players take turns trying to knock their assigned balls into the pockets while following specific rules about which shots are legal.