The item that we find here is clearly incomplete, and serving purely as a study piece for the purpose of practice. We find a thick trunk to the left hand side, and perhaps some elements of a pavement just behind. The lack of precision means it is hard to be too sure about what we are looking at, but it is likely that Gauguin never intended for this piece to be seen by the general public in any case, and saw it only as a means by which to work out some thoughts around a later artwork.
Gauguin was not classically trained in the way that others have been to various academics from a young age and learnt particular techniques that have set them up for successful careers. This was an artist who took an entirely alternative route, working in a number of professional jobs from a young age prior to turning his hand at art once these opportunities started to dry up. He always had an interest in art, but saw it more of a hobby before later throwing himself entirely into painting. He would also later turn his back on western society too, though kept some connections within Paris in order to help him sell on some of his work. With all this in mind, it was essential that he studied and practiced the techniques of drawing in order to fill that academic gap, and we find examples of that process here.
Visitors to the Tate to see this item will need to check first as it is not always on display. The institution also has a number of different galleries around which they spread their extensive collection and so it may not be on display where you expect. In recent years they have added galleries outside of London in order to allow more people to get to see some of these items without having to travel to the nation's capital. They have also created a selection which is wide ranging, and so can vary their offering to suit your taste, with the Tate Britain and Tate Modern being the best examples of this. Artists from around the late 19th and early 20th century have the ability to appear in both, with their styles being somewhere between traditional and contemporary art, which is also perhaps why they continue to enjoy considerable popularity amongst the general public.