It just means distributing your learning trough time, so basically the opposite of cramming.

I guess spaced repetition can be seen as a combination of distributed learning and practice testing.

I got the terminology from here

http://journals.sagepub.com/stoken/rbtfl/Z10jaVH/60XQM/full

Here is a nice summary of the results

http://journals.sagepub.com/na101/home/literatum/publisher/s...