The accessibilities open (or close) services for certain groups of people. It is e.g. about the fact that a service is only accessible for women*, or that the service can be taken under the influence of drugs, or not. If a service is meant for a certain target group, but is not closed to people outside this target group, this target group is set with the help of the 'themes'.
A service is also 'accessible' if it can be taken for free or for a donation. (Whereby donation means that theoretically there is no minimum price).
Accessibility in the sense of wheelchair-accessible is location-bound. You will find this info under 'Location' instead of 'Accessibility'.