Synchronous learning simply means that learners are engaged in learning at the same time. In today's world that could mean via traditional classroom methods or in an online environment. While a Synchronous online environment might be new to some, it has capabilities to continue learning when the traditional classroom setting is impossible or not desired.
Asynchronous learning happens on the learners schedule often with deadlines. Self guided modules, vidoes, recorded lectures are all forms of Asynchronous learning.