Some age considerations include making things safe, especially for the very young or the very old, or accessible, for instance a child can help set the table if the items that go on the table are placed within reach. Lowering the height of a bed can reduce dangerous falls for the elderly. And some aids can help with elders dealing with forgetfulness or dementia. For instance a black floor is perceived by some Alzheimer's patients as a hole in the ground and can keep them from wandering out of a safe area.
Then there are other types of age appropriateness, for instance teens who want a room that incorporates current trends and fashions into the place where they invite their friends.
Age appropriateness makes a difference in the activities that people will enjoy. Board games acknowledge that by giving the ages they are intended to amuse or for whom they are most appropriate. Some games provide good learning opportunities for children, or in some cases, even for adults.