Campaign url builder is a free tool by google. You can find this free tool here
What campaign url builder does:
If you own a website, a blog or an e commerce business and you post links on social media, you are making google search ads , display ads , facebook ads , with google url builder you can track many things on your google analytics account by setting a different name or a different identified parameter for each keyword, or source of traffic.
Campaign url builder looks like this (image below)

Example
We are going to cover a real example on a website that sells wall stickers , canvas prints , laptop stickers, door stickers , wall murals, etc.
When we create a google ad and we try to sell canvas prints we want to grab the destination link and put it on the website URL * field as shown in the image above.
If our landing page is https://yourwebsite.com/canvas-prints, then we want to paste that url in the first field. The next fields are filled by us manually. This means we can set whatever we want there. But the keywords you will put there will be the identifiers in your google analytics , this means that keywords will be shown on your google analytics. The main function of this tool is to help you understand how each channel performs. If you are very organized you can use this awesome tool to help you improve your conversions.

If you do own an e com business you should be using google utm builder in a smart way. It can drastically help you increase your conversion rates if you use it in a smart way!