UTM parameters are used to analyse the success of online campaigns. They also help to assign visitors to the correct channels (social, email, organic search, etc.) in Google Analytics. The UTM parameters (= bold) are appended to the actual URL, as in the following example:
https://zweipunkt.com/guide-erstellung-utm-parameter/?utm_source=newsletter&utm_medium=email&utm_campagin=utm-guide
So if you want to analyse the effectiveness of your own campaigns (paid or organic), you should use the UTM parameters.