An access point converts the wired network into a wireless WiFi signal. In an office there are usually several, spread across the floors. Together they form one network in which your device automatically picks the best signal (see roaming).
How many access points are needed depends on the floor area, the walls and above all the number of users. One access point can only serve a limited number of devices well at the same time.
An access point is only as good as the cable it is connected to. It often also gets power via that cable (see PoE). Read more in Office WiFi: why "we have WiFi" is not enough.
What does this mean for the IT-Label?
Access points fall under the Infrastructure component, as WiFi is explicitly part of it. Under Performance, the WiFi network is measured under real load, where people actually work. The better the coverage and capacity, the higher the label: IT1 requires strong WiFi coverage, IT1+ enterprise WiFi. See also WiFi survey and roaming.