Accessible means that disabled persons can, without assistance, approach, enter, pass to and from, and make use of a built environment without undue difficulties.

Providing easy access into and around buildings and public spaces is important for everybody but essential for disabled people.

In other words, access means:

Is a building accessible?
Does it comply with the Building Regulations?
Does Planning Permission require it to have an entrance ramp and disabled people's parking space?

It can also mean ... Is my home accessible and usable by me and my visitors?