A design pattern is a template in which application can be designed so that it will provide us the tight cohesion and loose coupling of the components/classes, so that the application can be extended/modified very easily for further use.

Designers gave us the templates so that the design can be picked up based on the requirement.

We can categorise these templates into three types based on type of use.,

1. Structural Design Patterns
2. Creational Design Patterns
3. Behavioural Design Patterns

Structural Design Patterns:

Structural Design Patterns are design patterns which simplify the way of entities related to each other.

Examples such as:

1. Adapter Design Pattern
2. Composite Design Pattern
3. Decorator Design Pattern
4. Facade Design Pattern
5. Proxy Design Pattern etc.,

Creational Design Patterns:

Creational Design Patterns are design patterns which simplifies the object creations based on the situation.

Examples such as:

1. Singleton Design Pattern
2. Prototype Design Pattern
3. Builder Design Pattern
4. Factory Design Pattern
5. Abstract Factory Design Pattern etc.,

Behavioural Design Patterns:

Behavioural Design Patters are patterns which makes design flexible and easier in communication between the entities created.

Example such as:

1. Template Method Design Pattern
2. Iterator Design Pattern.
3. Observer Design Pattern.
4. Command Design Pattern etc.,