Inflation is defined as a sustained increase in the general level of prices for goods and services. It is measured as an annual percentage increase
inflation is a sustained increase in the general price level of goods and services in an economy over a period of time. When the general price level rises, each unit of currency buys fewer goods and services.
Inflation occurs when the cost of goods and services increase over time.
Inflation cannot be measured by an increase in the cost of one product or service, or even several products or services. Rather, inflation is a general increase in the overall price level of the goods and services in the economy. 
The factors which affect them are :
1) Demand-pull inflation 
2) Cost-push inflation

Demand-pull inflation occurs when aggregate demand for goods and services in an economy rises more rapidly than an economy’s productive capacity. One potential shock to aggregate demand might come from a central bank that rapidly increases the supply of money.The increase in money in the economy will increase demand for goods and services.
Cost-push inflation, on the other hand, occurs when prices of production process inputs increase. Rapid wage increases or rising raw material prices are common causes of this type of inflation. The sharp rise in the price of imported oil during the 1970s provides a typical example of cost-push inflation.Rising energy prices caused the cost of producing and transporting goods to rise. Higher production costs led to a decrease in aggregate supply and an increase in the overall price level.