The word saw has two completely unrelated meanings:

1. A tool with a sharp, toothed blade used for cutting through wood, metal, or other materials. Carpenters use handsaws to cut boards, while lumberjacks might use chainsaws to fell trees. When you saw something, you move the blade back and forth across it until it cuts through. The teeth on the blade work like tiny knives, each one removing a small bit of material with every stroke. You might saw a piece of wood in half for a school project or watch your parents saw branches off a tree.
2. The past tense of the verb “see.” When you saw something, you observed it with your eyes in the past. “Yesterday I saw a hawk circling overhead” or “She saw her friend at the library last week.” This is one of English's irregular verbs, which means it doesn't follow the normal pattern of adding “-ed” to make the past tense. Instead of “I seed,” we say “I saw.”