The gas hose enables the cooker to be connected to the gas valve. In other words, it's the part that delivers the gas to the jets that supply the burners.
Are you smelling gas even though you're not using your cooker, or can actually see that your gas hose is damaged? In that case, you'll need to replace it as soon as possible.
Another possibility is that your gas hose has reached the end of its normal lifespan (e.g. 5 years, 10 years, etc.).
Find and order the right gas hose to fit your hob on our website. We have many different models available.