Muslims as a whole seek to practice sharia, as the word refers to the moral and religious regulations of Islam. However, "Sharia law" has become very politically charged as a term, representing the harshest and most conservative corners of Islamic thought.
Sharia law involves religious regulations regarding how to eat, how to have sex or how to distribute one's estate after death. In many small, devout Islamic communities throughout the world, sharia is used to settle intra-community disputes, but it is not treated as binding over people outside those communities.
"Sharia law" is sometimes used as a buzzword referring to a very conservative application of sharia as the law of the land. Some Islamic countries do not recognize any separation of religion and state, and use sharia as legally binding over all citizens, Muslim or not.