Money flow refers to the flow of money in terms of receipts and payments across different sectors of the economy. Flow of factor payments by producer sector to the household sector or flow of money from household sector to producer sector on account of the purchase of goods and services for consumption are examples of money flows.
Real flow refers to the flow of goods and services across different sectors of the economy. Flow of factor services from household sector to the producer sector or flow of goods and services from producer sector to household sector are examples of real flows.

Externalities refer to the benefits or harms that a firm or an individual causes to another for which they are not paid.
For example, river pollution created by an oil refinery has disastrous effects on aquatic life.
It reduces the overall welfare of the society and create negative externality.

Functions of a Central Bank:
A central bank performs the following functions, as given by De Kock and accepted by the majority of economists.

1. Regulator of Currency: The central bank is the bank of issue. It has the monopoly of note issue. Notes issued by it circulate as legal tender money. It has its issue department which issues notes and coins to commercial banks. Coins are manufactured in the government mint but they are put into circulation through the central bank.

Central banks have been following different methods of note issue in different countries. The central bank is required by law to keep a certain amount of gold and foreign securities against the issue of notes. In some countries, the amount of gold and foreign securities bears a fixed proportion, between 25 to 40 per cent of the total notes issued.
In other countries, a minimum fixed amount of gold and foreign currencies is required to be kept against note issue by the central bank. This system is operative in India whereby the Reserve Bank of India is required to keep Rs 115 crores in gold and Rs 85 crores in foreign securities. There is no limit to the issue of notes after keeping this minimum amount of Rs 200 crores in gold and foreign securities.
The monopoly of issuing notes vested in the central bank ensures uniformity in the notes issued which helps in facilitating exchange and trade within the country. It brings stability in the monetary system and creates confidence among the public. The central bank can restrict or expand the supply of cash according to the requirements of the economy. Thus it provides elasticity to the monetary system. By having a monopoly of note issue, the central bank also controls the banking system by being the ultimate source of cash. Last but not the least, by entrusting the monopoly of note issue to the central bank, the government is able to earn profits from printing notes whose cost is very low as compared with their face value.
2. Banker, Fiscal Agent and Adviser to the Government: Central banks everywhere act as bankers, fiscal agents and advisers to their respective governments. As banker to the government, the central bank keeps the deposits of the central and state governments and makes payments on behalf of governments. But it does not pay interest on governments deposits. It buys and sells foreign currencies on behalf of the government.
It keeps the stock of gold of the government. Thus it is the custodian of government money and wealth. As a fiscal agent, the central bank makes short-term loans to the government for a period not exceeding 90 days. It floats loans, pays interest on them, and finally repays them on behalf of the government. Thus it manages the entire public debt. The central bank also advises the government on such economic and money matters as controlling inflation or deflation, devaluation or revaluation of the currency, deficit financing, balance of payments, etc. As pointed out by De Kock, “Central banks everywhere operate as bankers to the state not only because it may be more convenient and economical to the state, but also because of the intimate connection between public finance and monetary affairs.”
3. Custodian of Cash Reserves of Commercial Banks:Commercial banks are required by law to keep reserves equal to a certain percentage of both time and demand deposits liabilities with the central banks. It is on the basis of these reserves that the central bank transfers funds from one bank to another to facilitate the clearing of cheques.

Voluntary Unemployment - Voluntary unemployment refers to a situation where a person who is able to work remains unemployed due to his/her own willingness. Under this situation, the person remains unemployed despite jobs being available in the market.
Involuntary Unemployment - Involuntary unemployment refers to a situation where a person who is willing and is able to work does not get work at the existing wage rate. Under this situation, the person remains is unemployed due to non-availability of jobs in the market.