what might be the reason for this? And this horrible thing won’t move.
p.s. I’m a beginner
These are pixols/pixels, which are part of the image Document. You can clear them with Ctr+n.
As for why this happens:
Zbrush is a painting program at its heart, with a lot of similarities between other painting programs (so think of it more like photoshop or ms paint instead of a 3d program like Maya). You create a document with an X & Y resolution, select a Tool from the Tool palette (be it a paintbrush or a 3d polymesh), select a color from the Color palette, adjust the Draw settings, and then draw the Tool onto the Document to modify the values of its pixels.
Whenever you draw something onto the zbrush document, as soon as you release the mouse button then whatever you just drew is put in a temporary waiting state while zbrush waits to see what you do with it. Zbrush gives you a chance to Transform what you just drew by using the Move, Scale, Rotate or Edit options (note: the Edit option is only available for 3d models). If you do anything other than select one of those four options (for example, if you select a different Tool or make another canvas stroke - even an empty click of the mouse) then your old stroke becomes permanently fixed to the canvas so that the new one can enter the waiting state. If you’ve drawn a series of spheres, you won’t be able to select any of your previously drawn spheres: they have been dropped to the canvas. They are now pixels on the document, part of the global illustration.
Little more than an image, which is why they can’t move or rotate.
This dropping to the canvas will happen with any 3D model, either one made inside ZBrush or imported from another software package. But don’t worry; if you want to work on a model in its 3D form all you have to do is switch on Edit mode immediately after drawing the model onto the document. Then you will have access to all the 3D sculpting and painting tools. And if you should accidentally turn off Edit mode while working, your 3D model will still be available in the Tool palette; simply clear the canvas with Ctwl+N, re-select your Tool, click-drag to draw it on the canvas (the drag rect stroke type can help), and then turn on Edit mode to continue working on your sculpt.