Understanding developmental groove in teeth

[Akam ahz]

Hello,
I'm a first year dental student, and in my dentition book I came across the topic of "crown depressions" in which the author says about the developmental groove in posterior teeth:

"Grooves act as spill ways for cusps during lateral and protrusive jaw motions."

I don't get the sentence above, so an explanation in a simple language would be great.

Thanks in advance!

 

[schmoob]

Just think of the posterior grooves as sort of "the roads" that your cusps travel along protrusive and laterotrusive movement.