Fuel means substance which burn to give energy but combustion is a process of burning

Fuel:
Fuel is a substance that is used to produce energy through combustion. It is a material that releases energy when it undergoes a chemical or nuclear reaction. Fuels are commonly used for powering vehicles, generating electricity, and heating homes and industries. They come in various forms, such as solid, liquid, and gas.

Combustion:
Combustion is a chemical reaction between a fuel and an oxidizing agent, usually oxygen, which results in the release of energy in the form of heat and light. It is a rapid oxidation process that occurs when the fuel combines with oxygen in the presence of a spark or heat. Combustion is an exothermic reaction, meaning it releases energy.

Difference:

1. Nature:
- Fuel is a substance that can be burned to release energy.
- Combustion is the chemical reaction that occurs when a fuel reacts with an oxidizing agent to produce heat and light.

2. Role:
- Fuel acts as the source of energy.
- Combustion is the process by which the energy stored in the fuel is released.

3. State:
- Fuel can exist in solid, liquid, or gaseous state.
- Combustion is a chemical reaction that occurs when a fuel is in contact with an oxidizing agent, usually oxygen.

4. Energy Release:
- Fuel contains potential energy which is released during combustion.
- Combustion releases the stored energy in fuel in the form of heat and light.

5. Dependency:
- Combustion cannot occur without a fuel.
- Fuel can exist without combustion if it is not exposed to an oxidizing agent.

6. Examples:
- Examples of fuels include gasoline, diesel, coal, natural gas, and wood.
- Examples of combustion include burning of a matchstick, lighting a candle, or operating a car engine.

7. Purpose:
- Fuels are used to power vehicles, generate electricity, and provide heating.
- Combustion is the process by which the energy stored in the fuel is converted into useful work or heat.

In conclusion, fuel is the substance that is burned to release energy, while combustion is the chemical reaction that occurs when fuel combines with an oxidizing agent to produce heat and light. Fuel acts as the source of energy, while combustion is the process by which this energy is released. Fuels can exist in various states, while combustion requires the presence of an oxidizing agent.