When a browser or bot requests a webpage, it sends a “Referer” HTTP header containing a URL of the page that they were previously at, if they followed a link there. It is based on a canonized misspelling of the word “referrer”.

So, if you are on website1.com, and you follow a link from there to website2.com, the administrators of website2.com will be able to see you came there from website1.com based on the string that was passed in the Referer header.

To prevent this from happening, you can just configure your browser to send a different Referer, or even no Referer at all!

Since Referer strings are set on the application level, how to spoof it depends on the type of software you are using. If you have multiple programs, you will have to spoof them all individually:

Use the -e or --referer flag to directly set the Referer:

$ curl --referer "http://comes-from.example.com" https://www.example.com
- or -
$ curl -e "http://comes-from.example.com" https://www.example.com

To send a blank Referer:

$ curl -e "" https://www.example.com

Since the Referer is passed as an HTTP header, you can also change the Referer header by using the -H or --header flag, which lets you manipulate headers:

$ curl --header "Referer: http://comes-from.example.com" https://example.com
- or -  
$ curl -H "Referer: http://comes-from.example.com" https://example.com

To set a custom Referer header with Wget, use the --referer flag:

$ wget --referer="http://comes-from.example.com" https://example.com

For more information on how to use wget, read the Wget article.