Isolated and non-isolated DC-DC converters are two different types of power electronic devices used to convert one DC voltage to another DC voltage.  They serve different purposes and have distinct characteristics:

Isolated DC-DC Converters: 

• Purpose: Isolated DC-DC converter provide electrical isolation between the input and output voltage.  This isolation can be important for safety and to break ground loops in certain applications.
• Operation:  They use a transformer to achieve electrical isolation, which allows for voltage conversion while maintaining a physical separation between input and output circuits.
•  Advantages: Safety.  The isolation helps prevent electric shock and protects sensitive equipment from voltage spikes and noise.  Ground loop prevention.  They can help eliminate ground loop problems in applications where multiple ground references exist.  Voltage regulation.  Isolated converters can provide precise output voltage regulation.
• Disadvantages:  Complexity and Cost.  The inclusion of a transformer and additional circuitry can make isolated converters more complex and expensive.  Efficiency.  They are generally less efficient compared to non-isolated converters.

Non-Isolated DC-DC Converters:

• Purpose: Non-isolated DC-DC converters are used for voltage conversion without electrical isolation.  They are typically smaller, more efficient, and less expensive than isolated converters.
• Operation: Non-isolated converters do not use transformers for isolation and are typically based on topologies like buck, boost, or buck-boost converters.  The input and output share a common ground reference.
• Advantages: Efficiency.  Non-isolated converters are generally more efficient due to the absence of a transformer.
• Compact size.  They are typically smaller and lighter, making them suitable for space-constrained applications.  Lower cost.  Non-isolated converters are often more cost-effective.
• Disadvantages:  Lack of Isolation.  They do not provide electrical isolation which can be a limitation in certain applications where isolation is necessary. 

Applications for each type of converter depend on specific requirements:

• Isolated Converters are commonly used in applications where safety, isolation, and precise voltage regulation are crucial, such as in medical devices, industrial equipment, and some power supplies.
• Non-Isolated Converters are more suitable for applications where cost, efficiency, and size are primary concerns, like in battery-powered devices, automotive electronics, and many consumer electronics.

The choice between isolated and non-isolatedd DC-DC converters depends on the trade-offs that best meet the needs of a particular application,