What you are asking is ‘Referrals’ to your website. Traffic analytics software will show you referrals. From there look at the referrals that are from other websites and there you will find your answer.
Any analytics program can help you with that. Your web hosting provider should give you access to monitor traffic to your website, such as Webalizer or AWStats. Google Analytics is the go-to option that is free and gives you tons of insights once you know how to use it.
The opposite is a little bit more tricky. Detecting what traffic goes from your website to another website. This is important to know if you have paid banners on your website. To give you an idea of how many clicks your banner gets that go to a website will help you determine how well that banner is doing. To find this out you add a little bit of code to the end of a link that looks like this.
Everything after the question mark (?) is a tracking code to help you find out the answers you need. Here is a link that helps you generate the tracking code that you need.
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