How is prayer different in Buddhism when compared to theistic religions?

We all know the concept of kamma-vipaka and that we should strive and create the causes of our happiness. I understand the Buddhas only point the way, they teach the Dhamma and we are responsible for walking the path. In this context, why it is so commom for Buddhists to pray? For example, does prayer in Buddhism have a different meaning when compared to for example Christianity? I can understand why praying is so important in religions with a creator God, because that is the way you ask for all sorts of blessings, but in Buddhism it is not so clear, does praying have a different meaning or purpose?