It is a serigraph artwork, which means that it is a silk screen print using ink onto a piece of heavy weight paper.
Firstly, the artist paints or draws onto the mesh of the silk screen, and then they press a substrate (in this case, thick paper) onto the screen to create a clean, clear impression.
Though it might seem at first sight to be just a simple squiggle, looking at it more closely demonstrates that this is unmistakeably a work by Picasso.
Picasso's Horse Drawing falls into the category of 20th centry Primitive art. In this case, Primitive art simply means artworks that deploy simple, minimal lines to evoke a recognisable form.
It could be argued that in this drawing Picasso used the minimum number of lines possible to suggest the shape, movement and musculature of a powerful horse standing alert. This Primitive style is to be distinguished from the movement in Western art known as 'Primitivism', which also was in vogue in the first half of the twentieth century.
The Primitivists were Western artists who borrowed shapes and symbols from what they considered to be 'primitive' peoples. One example is the painter and sculptor Paul Gauguin, who used Tahitian motifs in his works.
This is by no means the only work of art that Picasso created that involved a horse. Indeed, he seems to have been fascinated by these animals.
Famously, a silently screaming horse features in his epic pacifist art work 'Guernica', for instance, and an early (1906) study entitled 'Boy Leading a Horse' depicts a peaceful scene involving a naked boy and a grey horse towering to his side. Picasso's painting 'Bullfight', moreover, focuses less on the eponymous bull and more on the horse.
This horse, stamping the ground in what could be fury or distress, has unseaed its rider and may be said to be one of the victims of the fight.
Though throughout his oeuvre Picasso tends to depict horses in moments of extreme or overwhelming pain or emotion, his calmer studies can often be jauty or jovial. This drawing of a horse is a prime example of this: a skilled artist demonstrating his skill and showing his love of the equine form with a few minimal lines.