Time series - meaning, components and examples, methods

Time series is the arrangement of data according to time of occurrence.

There are a few factors that are responsible for bringing about changes in a time series data. They are known as the components of time series.
The components:
1.Secular movements
2.Seasonal movements
3.Cyclical movements
4.Irregular movements

Secular movements are also known as secular trends. They are the long term variations. These variations take a long time to happen.
Example: 
Expansion of technology and increase in the quality of commodities.

Seasonal movements or seasonal variations are the short term variations. The variations takes time periods like the seasons(generally, 3 to 6 months to be approximate).
Example:
Increase in the sale of umbrellas during the rainy season.

Cyclical movements are like business cycles. The variations rise and fall. They follow a pattern of prosperity, decline, recession and a boom.
Example:
An up and down of the sales of a business due to a few reasons.

Irregular movements are also known as erratic variations. As the name suggests, the variations happen irregularly. Generally, the causes are natural disasters. 
Example:
Shutting down of a small restaurant due to it's destruction from a tsunami.

3 methods to calculate the time series:
1.Semi average method
2.Moving average method
3.Least square method