What does transpiration mean?

Transpiration is the release (evaporation) of water from a plant, typically through the undersides of its leaves. This is for the same purpose as perspiration in some animals: to cool the plant. It also keeps the stomata (pores) open for carbon dioxide to enter. The water flow from the roots to the leaves carries minerals to the plant tissues.

Plants absorb water through their roots and then give up water vapour through the pores in their leaves.

Kid's bite-sized explanation

Transpiration is most similar to sweating in humans. Transpiration cools plants beginning from the roots, outward through the leaves. But rather than seeing it, like humans get sweat on their skins, plant's transpiration (sweating) is more of a vapor.