An access point is a connection between wireless devices and router. The router is connected to devices in a local area network (LAN). Wireless devices include smartphones, laptops, tablets, etc.
If your laptop is connected through an access point to the LAN then you can get access to the printer that is connected to the LAN. Some modems and routers have built-in functionality of the access point. Modern access points do not have visible antennas and antennas are build inside the device.
Access points are better for business use because they need more connection to devices. There are two main terms to be considered to this topic:-
Range extender extends the range of the WIFI router. It is connected to the location where the signals of the WIFI router is strong. If you have a WIFI router placed on the ground floor then range extender should also be placed there. If your devices are located on the 1st or 2nd floor then the range extender (that is placed on the ground floor) gives good signals also.
Some modems act as wireless routers that connect wired and wireless devices to form a local area network. The devices can communicate with each other in the LAN with the router but for communicating with other devices (outside LAN) you need access point (AP)
Access points are used to increase the number of devices communicating with each other. If you want to organize an event where thousands of devices need to be connected then it is best to use access points. You can connect about 60-80 devices with one access point. So for connecting more than 60-80 devices you need another access point and so on.
Range extender and the wireless router are good for home use or for a small office where fewer devices are connected but the access point is for business use.
Routers give extra security of firewalls and password protection to the LAN. If any data coming from a wireless device to the LAN then it is first filtered out with a router.
WIFI devices can connect up to 20 devices simultaneously. For more devices to connect it is better to use access point (AP).
Access point (AP) is sometimes called as wireless access point (WAP) also.