Nelio A/B Testing adds a few parameters in your URLs. These parameters tell Nelio A/B Testing which variant has to be loaded for each visitor. For instance, if you created a headline test for your Foo post and added two alternative headlines, you’ll end up having the following URLs:
https://example.com/foo/?nab=0
is variant A (the control version)https://example.com/foo/?nab=1
is variant Bhttps://example.com/foo/?nab=2
is variant C
Thus, if a user accesses http://example.com/foo/?nab=1
, she’ll see the alternative headline:

Hiding/showing split testing arguments
Nelio A/B Testing loads alternative content by adding a few parameters in your URL. In principle, these parameters are visible to your visitors, but you can decide whether they should be hidden or not

If you check the A/B Query Args setting, once the alternative content has been loaded, all A/B Testing parameters will be removed from your URLs.
Keep in mind that these parameters will be visible in your Google Analytics results. Learn how to instruct Google Analytics to ignore some of these parameters so that they don’t mess your reports.