Mixed economy is an economic system that includes a variety of public and government control, or a mixture of capitalism and socialism.
There is not one single definition for a mixed economy, but relevant aspects include: a degree of private economic freedom (including privately owned industry) intermingled with centralized economic planning and government regulation (which may include regulation of the market for environmental concerns, social welfare or efficiency, or state ownership and management of some of the means of production for national or social objectives).
Technically all the economies of the world are mixed: it is just the balance elements between market and planned elements that alters.
The aim of mixed economies is to avoid essential disadvantages of both systems while enjoying the benefits that they both offer. So, in a mixed economy the government and the private sector interact in solving economic problems. The state controls the share of the output through taxation and transfer payments and intervenes to supply essential items such as health, education and defence, while private firms produce cars, furniture, electrical items and similar, less essential products.
The UK is a mixed economy: some services are provided by the state (for example, health care and defence) whilst a range of privately owned businesses offer other goods and services.