Why alcohols are soluble in water?

It's because of how their molecules are built. Think of water molecules like tiny magnets. They stick together really well.

Alcohols have a special part called an -OH group. This part is also like a little magnet, so it's very attracted to the water molecules. This attraction is strong enough to pull the alcohol molecules in and mix them all up with the water. This is called hydrogen bonding.

But, alcohols also have a carbon chain part that doesn't like water. For smaller alcohols, like rubbing alcohol, the magnet-like -OH part is strong enough to make it dissolve. If the carbon chain gets really long, that part wins, and the alcohol won't mix with water anymore.