What is Samskara?
Who you think you are, your identity, as well as the entire world you live in, is a product of your Karma or actions. The nature of Karma is that it leaves behind the impression or Samskara, an idea from which arises another desire, or modifies the original desire. This Samskara is the seed for further action.
Everything you do, although it seems like you are personally involved in deciding your action, is simply happening as a series of reactions due to samskaras. In reality, you are not making any choices, Samskaras are. For example; you eat because you are hungry, an action based on a desire (perhaps the desire to survive) however--if a particular food makes you sick, you are left with a particular impression, one that will influence your future actions in relation to that food. In the future, you will avoid, or not even "like" the particular food which caused you discomfort. Thus, the course of your future actions and your identity itself is modified. All future actions related to that food is now "colored" by your Samskara. While you think you have free will in deciding what to eat, you are simply reacting from Samskara.
Our personal actions, our societies, cultures, and even the world itself are nothing more than a reflection of an ever evolving and increasingly complex web of many Samskaras.
In this cycle, we have no freedom and we are bound to our Karma.