While your IP address identifies where you are on the Internet, your MAC address identifies which device you are using on the local network. MAC addresses are only useful on the local network and are not sent over the Internet.
1. If you use your laptop to connect to several Wi-Fi networks, the same MAC address of your Wi-Fi interface is used on all those local networks. Someone observing those networks can recognize your MAC address and **track your geographical location**.
MAC address anonymization is enabled by default in Tails because it is usually beneficial. But in some situations it might also lead to connectivity problems or make your network activity look suspicious. This documentation explains whether to use MAC address anonymization or not, depending on your situation.
**Using your own computer on an public network without registration**, for example a free Wi-Fi service in a restaurant where you don't need to register with your identity. In this case, MAC address anonymization hides the fact that your computer is connected to this network.
Other means of surveillance can reveal your geographical location: video surveillance, mobile phone activity, credit card transactions, social interactions, etc.