Use of sprays in differential geometry?

Question

I have been reading Fundamentals of Differential Geometry by Serge Lang. In his treatment, the notion of sprays plays a central role. However, I rarely see this term in other books on the subject.

Although this is a soft question, I try to make clear my questions:

1. Is spray a somewhat out-dated notion?
2. What is the geometric meaning of sprays? (This name is suggestive but I don't have any intuition for it...)
3. What are the advantages and disadvantages of using sprays?
4. Can you suggest an alternative book whose treatment is similar to that of Lang's and which is modern and readable?

Thanks in advance!