Short answer
Sharia means the path or way, and it is the whole guidance of Islam for how to live: worship, honesty, family, business and justice. Only a small part of it is criminal law. Most of it is about how a Muslim prays, gives charity and treats others.
The fuller answer
Sharia comes from the Quran and the Sunnah, and is expressed in fiqh, the human understanding of the scholars about how to apply it. That is why the four schools of Sunni law and others sometimes differ. Sharia is not one fixed code written in a book: it is a body of rulings that scholars derive with evidence.
For a Muslim living in a non-Muslim country, Sharia mostly means personal obligations such as prayer, fasting and honest dealing, and there is no wish in most communities to replace the local law. Muslims differ widely about how much a state should apply it. You can read the main rulings, with their evidence, in the Fiqh section of this website.
This answer follows the mainstream Sunni understanding and is general learning, not a fatwa. Where Muslims differ, the answer says so. Have a question of your own? Write to us.