Access is the ability to use a service, information, or other resource.
It can describe a state that occurs in a transaction:
The system granted access to the requested file.
It can describe a continuing entitlement:
All staff members have access to the email system.
To access is to obtain permission to use a controlled resource.
Accessing a system usually involves authentication as a precursor to obtaining authorisation. For this reason access is sometimes used as a synonym for ‘login’.