That's the "brush leash", which is part of the new brush stroke smoothing feature in CC2018. The leash shows you where your brush stroke will land when you have smoothing enabled. If you don't like it you can either disable smoothing by clicking not he brush tool and then entering "0" in the "Smoothing" box that appears in the top menu OR turn off the brush leash itself in preferences:
A short video with more info on the smoothing brush is here: How to use Brush Stroke Smoothing in Photoshop CC 2018 - YouTube
Additional info on brush stroke smoothing (including turning off the purple line). This comes direct from Adobe, so it should be available in Spanish also: New features summary | October 2017 release of Photoshop CC.