Sawyer (2005) defines "Implicit Learning" as:
Implicit learning refers to situations in which complex information is acquired effortlessly (without a conscious effort), and the resulting knowledge is difficult to express verbally (e.g., Berry, 1997; Cleeremans, Destrebecqz, & Boyer, 1998; Reber, 1967 ). Although many types of implicit learning exist, a common process underlies most of them - the rapid, effortless, and untutored detection of patterns of covariation among events (Reber, 1993). (Page 19)
Also, this Wikipedia article provides a nice definition of it.
Soderstrom and Bjork (2015) have defined "Latent learning" as:
Latent learning is defined as learning that occurs in the absence of any obvious reinforcement or noticeable behavioral changes. Learning is said to be “latent,” or hidden, because it is not exhibited unless a reinforcement of some kind is introduced to reveal it. Consider, for example, a person who recently moved to a new city and, apprehensive about driving, decides to ride the city bus each day to work. Riding the bus day after day, the route would be learned through observation, but such learning would only be evident if an incentive was present that required it—say, when it was necessary for the person to drive to work on his or her own. The early findings of latent learning were intriguing and controversial because they challenged the widely held assumption that learning could occur only in the presence of reinforcement. For a classic review of the early latent learning studies, we recommend Tolman (1948), in which the concept of “cognitive maps” was introduced, a term that refers to the mental representation of one’s spatial environment. (Page 177)
What is the difference between these two?
Sawyer, R. K. (Ed.). (2005). The Cambridge handbook of the learning sciences. Cambridge University Press.
Soderstrom, N. C., & Bjork, R. A. (2015). Learning versus
performance: An integrative review. Perspectives on Psychological
Science, 10(2), 176-199.