WiFi hotspots can be open or secure. If a hotspot is unlock, then anyone with a WiFi card can access the hotspot/ Acssespoint . If it is secure, then the user needs to know a WEP key /the Network Key to connect.
WEP stands for Wired Equivalent Privacy, and it is an encryption system for the data that 802.11 sends through the air. WEP has two variations: 64-bit encryption (really 40-bit) and 128-bit encryption (really 104-bit). 40-bit encryption was the original standard but was found to be easily broken. 128-bit encryption is more secure and is what most people use if they enable WEP I can recommend it also .
For a casual user, any hotspot that is using WEP is inaccessible unless you know the WEP key.
If you are scenery up a hotspot/Accesses point in your home, you may want to create and use a 128-bit WEP key to prevent the neighbors from casually eavesdropping on your network.
Whether at home or on the road, you need to know the WEP key, and then enter it into the WiFi card's software, to gain access to the network.