Federal law is the whole of the laws passed by the federal government of a country. The federal government is the government that runs the entirety of the country, rather than governments at a smaller level such as state, province, or city. Federal law is typically established in one or more documents that clearly indicate the laws that govern the whole of the country, and may be created and upheld by one or more departments within the federal government. In the United States (US) for example, federal law is created by Congress, upheld by the president, and interpreted and enforced by the Supreme Court.
US law consists of the US constitution, US treaties, federal common law, and federal statutes and regulations. This makes up the body of law for the whole of the US and all citizens within the nation are considered equally protected and governed by these laws. Due to the separation of powers between different levels of government, these laws will usually not deal with any of the rights reserved for state governments.
While federal law may govern the overarching activities of all citizens of a country, as well as regulating various government agencies, it may not include all the laws of all regions within the country. In the US, states have certain powers and pass laws regarding how each state will be run, as well as state issues such as state parks, education, and transportation. Federal government laws, however, deal with delegating what rights states have, as well as dealing with any issues of injustice or offense between one or more state governments.
According to most readings of the US Constitution, federal law overrules state law if there is a conflict between the two. Article IV, Section 2 of the Constitution gives the people of each state all the same rights as those enjoyed by all the people within the country. This is seen as ensuring that no state can pass a law that eliminates or hinders the rights guaranteed by these laws and is typically upheld as such by the Supreme Court.
In smaller countries, however, federal law may be a more specific matter that does govern the daily actions of its citizens. Countries with fewer regions may only have federal laws and city laws, instead of breaking the power structure down into other levels. Because of the large and sweeping nature of powers granted by these laws, care should be taken to ensure that abuses are not made and that tyrannical laws are not passed.