The term 'PERIOD, IN WEB ADDRESSES' is referring to the use of a period (or DOT) in web addresses. A period is used to separate different parts of a web address, such as the domain name and the top-level domain. For example, in the web address www.example.com, the period separates the domain name 'www' from the top-level domain '.com'. The period is an essential part of web addresses and is necessary for a web address to be valid.