Common law (also known as case law or precedent) is a law largely formed by the decisions previously made by courts and not imposed by legislatures or other government official. Therefore, it is not found in a written form compared to statutory law. Common law system is a legal system that gives great precedential weight to common law, on the principle that it is unfair to treat similar facts differently on different occasions. It is the body of precedent and binds future decision. 
The term “common law” also underlines the fact that this type of law did not originate from equity, maritime and other special branches of law. 2] The type of reasoning used to interpret this law is known as ‘case-based’ reasoning, which is a strict, principle-based reasoning that uses the circumstances of a case to evaluate the laws that are applicable. Common law judges rely on their predecessors’ decisions of relevant courts rather than on abstract codes or texts, to guide them in applying the law.  They find the grounds for their decisions in law reports, which contain decisions from the past (this principle is known as stare decisis).
If common law judges hear a case that has a new issue in it (called a “matter of first impression”), the judges have the authority to make law by creating precedent, which then must be followed by other courts with equal standing within the legal system. The precedent remains law unless and until a higher court overturns the decision. In most cases, common law applies only within that jurisdiction. Judges often create common law by writing opinions about cases that bind lower courts in that jurisdiction. The foundation for this type of law is formed by torts, property and contracts.
A court’s decision is binding authority for similar cases decided by the same court or by lower courts within the same jurisdiction. The decision is not binding on courts of higher rank within that jurisdiction or in other jurisdictions, but it may be considered as persuasive authority.  The advantages of common law within the legal system is that equity is a characteristic of this system. This is because all people (irrespective of their position, wealth or power), are treated equally as the precedents are followed in all cases.
It tends to bring up equity and fairness to all people. Besides, common law is more expedient and efficient because the decisions made are based on previous judgements. The process would be much more easier, practical and faster as it is based on real situations that have already been resolved. It guarantees predictability and certainty. On the other hand, common law is slow to evolve. Landmark decisions (from which new principles develop) are few and far between. They usually arise from cases on appeal heard in the highest courts.
Because these precedents are to be followed by all other courts or in many cases, lengthy, detailed records have to be maintained. And to make easy the accessing of these cases and previous decisions, uniform indexing methods have to be created and followed diligently. Legislation is known as one of the three main functions of government. Separation of powers divided into three separate branches. i. e. Executive, Legislature, Judiciary.  They are also known as primary legislation.  Legislation is law which has been enacted by a legislature or other governing body, or the process of making it.
Another source of law is judge-made law or case law. Legislation can have many purposes: to regulate, to authorize, to proscribe, to provide (funds), to sanction, to grant, to declare or to restrict. After the legislation law has been enacted, it is known as Act of Parliament. Act of Parliament is a statute enacted as primary legislation by a national or sub-national parliament. Legislation is usually proposed by a member of the legislature. e. g. a member of Parliament, or by the executive. Then it is debated by members of the legislature and is often amended before passage.
Before an item of legislation becomes law it may be known as a bill, and may be broadly referred to as “legislation” while it remains under consideration to distinguish it from other business. Once it referred on to the Governor, the bill becomes an Act and will come into operation on a date proclaimed by the Governor. Subsidiary legislation, also known as Delegated legislation is law made by an executive authority under powers given to them by primary legislation in order to implement and administer the requirements of that primary legislation.
It is law made by a person or body other than the legislature but with the legislature’s authority. Delegated legislation fills in the details, when an Act of parliament sets out broad principles of regulation. They are also known as secondary legislation. There are various review and scrutiny committees attached to parliament to examine delegated legislation to make sure that it doesn’t go beyond the authority given under the enabling legislation.
The main advantage of legislation is that it is made by parliament and therefore reflects the will of the people insofar as members of parliament are democratically elected. The main disadvantage is that the words and terms used in Acts of parliament may be subject to several interpretations, rendering it unclear or ambiguous in a given fact situation. Delegated legislation has as many advantages as disadvantages. It is criticised for its increasing complexity in modern times. It is sometimes difficult to access which contradicts the assumption that ignorance of the law is no excuse.
Delegated legislation is made in some circumstances by persons of bodies who are not elected representatives. e. g. council rules, regulations and bylaws. There is always the risk that a delegated body may exceed the authority delegated to it under enabling legislation. Common law are judicial decisions whereas legislation is made by parliament. Common law promotes justice and fairness as well as guarantees predictability and certainty. Legislation, however reflects the will of the people and the decision is determined by the members of parliament.