Every web site is managed by a web server. The web server receives requests from visitors, and sends the requested pages to the visitors.
Each web server keeps a log of the requests it receives. This access log contains a line for each request. On each line is the IP address of the visitor, the time and date the request was received, the file that was requested, and the HTTP status code that was sent in response.
The access log gives me a crude way to see roughly how many visitors I've had, and which pages and files are the most frequently requested. The access log does not contain any sensitive data about visitors, nor does it identify the name or location of any visitor. (In fact, the logs are so crude that they don't even really allow me to be sure which requests came from real humans and which came from robot software.)