A router connects two separate networks together, either with or without the same media. An access point, when referred to in wireless terms (commonly), is basically an ethernet to wireless bridge. Some APs can incorporate routing algorithms and separate the bridge between the ethernet and wireless interfaces; however, it needs to be stated that technically they operate in separate OSI layers.
The wireless operates on layer 2 (and to some degree the first layer is different as well), the router operates in layer 3. A router + switch is layers 2 and 3 - so you can relate it, basically, to that.
Hope that helps.