An adaptation is a body feature or behavior that helps a living thing survive in its habitat. A polar bear's thick fur is an adaptation for cold weather. A cactus storing water is an adaptation for dry deserts. Over many generations, living things develop adaptations that help them survive where they live.
Show pictures of animals with obvious adaptations (duck's webbed feet, giraffe's long neck, chameleon's color-changing skin) and ask what each feature helps the animal do. Play a matching game: match the adaptation to the habitat. Try to "camouflage" paper butterflies against different backgrounds.
Have you ever wondered why a polar bear is white? Or why a cactus is covered in spines instead of leaves? Or why a duck has webbed feet? These are all adaptations — special features that help living things survive in their particular habitat.
An adaptation can be a body feature. A polar bear's thick white fur keeps it warm in the freezing Arctic and helps it blend in with the snow. A cactus has a thick stem that stores water and spines instead of leaves to reduce water loss — perfect for surviving in a dry desert. A cheetah has long legs and a flexible spine that let it run faster than any other land animal — great for catching prey on the African plains.
An adaptation can also be a behavior — something an animal does, not something its body has. Birds that fly south for the winter are showing a behavioral adaptation: they move to warmer places where food is available. Some animals hibernate (sleep through the winter) to save energy when food is scarce. Squirrels bury nuts in the fall to have food during winter. These behaviors are adaptations just like body features.
One really important thing to understand: adaptations do not happen in one animal's lifetime. A giraffe does not grow a longer neck by stretching. Instead, over many, many generations, the animals with features that helped them survive tended to have more babies. Those babies inherited the helpful features, and over thousands of years, the features became more extreme. This is how a polar bear's ancestors gradually got thicker and whiter fur, and how a giraffe's ancestors gradually got longer necks.
Every living thing you see is packed with adaptations that help it survive in its specific habitat. When you look at an animal or plant and wonder "why does it look like that?" — the answer is almost always an adaptation.