You can implement different kind of tools to measure traffic for you. You paste in some lines of code and you can see who visited your site from what country and from where. Like that person came from Facebook and that came from Reddit, Steemit, etc. Even in real time. For how long they were on your site, what pages did they check, what keywords did they type into search engines before they arrived to your site, etc. The most famous is Google Analytics. If Google Analytics showed a number of 100k visits for the last 30 days for me when I logged in(on my end), then when I checked my site on trafficestimate, I got a result of around 10-50k visits.

But there are lots and lots of free and paid traffic measuring tools. It's a must for every website to know how the changes you made affected the behaviour of the people visiting your site. So you can double down on the things that work, and forget the things that aren't. These tools are really useful.