Speed Is Distance Dependent
The farther the distance between transmitter and receiver, the lower the bit rate in an 802.11 system. (Chart courtesy of Intersil Corporation.)
In "infrastructure" mode, the laptops transmit to access points. In "ad hoc" mode, the laptops can communicate with each other directly in a peer-to-peer fashion.
These are 802.11g products from Linksys. The access point is connected to the network, and the wireless adapters are inserted into the client machines. Although most people think laptops when they talk about wireless, adding wireless to a remote desktop computer eliminates the need to run cables. (Images courtesy of Cisco Systems, Inc.)
Learn more about 802.11