I am new to AEM and know that AEM is based on pages. I am wondering if there is any functionality available using which an Author can create a common content snippet once and reuse on multiple pages. Please suggest.
This depends on the scope of reuse, you have option of:
Experience Fragments are much better due to cache management in 6.3.
It all depends on use case but there are several answers and approaches so you will need to pick the best fit for your project.