A neuroma is an enlargement of a nerve and usually involves some thickening / scarring around the nerve. In the foot small nerves run between the bones in the ball of the foot to supply sensation to the toes. When these nerves become enlarged or inflammed the condition is termed Morton’s neuroma after the clinician who originally described the problem.
This book is an excellent resource and, at £2.62 is well worth it for anyone suffering from this condition.