Beginning with what comes to mind first, it's very important that a home be accessible for the people living in it plus anyone who visits that home - regularly or not - to be able to approach the front door without any type of interference or hindrance, to open the door or have it opened for them from the inside, to walk through the doorway under their own power or with the aid of some type of mobility assistance, and to arrive safely on the inside.
For those already in the home - the residents or those visiting - reversing the process to safely and easily go outside and continue on their way is equally important. Often, we think just about getting into a home and devote less thought to how someone leaves a home and goes on their way.
A second major meaning of accessible is how easy it is for someone to move about and maneuver in a space. This freedom of movement describes accessibility even more than being able to enter a residence. Once inside, a person needs to have the freedom, flexibility, and ability to navigate passageways and travel from place-to-place without encountering any challenges that would hamper that movement. Anything that shrinks or reduces that freedom of movement hampers accessibility on the inside of a dwelling.
Then, a third meaning of accessible involves the ability for people to reach objects in the home - regardless of whether they are standing or seated. This applies to switches, controls, faucets, window hardware and sashes, drawers, door handles, shelves, closet rods, and anything in the home that requires that it be touched or grasped to operate it or get full utilization from it.
Reach is extremely important inside the home because any limitation in range of motion or grasping ability that make using controls, switches, fixtures, appliances, and similar items in the home would detract from someone's ability to benefit from what that home had to offer and could compromise their overall enjoyment and quality of life in that home.
Keep in mind that the idea of being accessible has at least these three major aspects to it that we need to remember in creating successful aging-in-place homes.