While statics lists are lists that you create manually or import, either by adding existing contacts or importing new ones, dynamic lists are created intelligently by adding and removing contacts that fit a set of criteria you define.
This allows you to maintain updated lists of connections which have responded to one of your previous engagements, subscribed to one of your outreach lists, connected with you in a certain time frame, or reside in a certain area. By mixing and matching requirements, you can create hyper-targeted customer segments and deliver personalized messages sure to resonate with each of your contacts.