When I turn on the switch, I could hear the noise coming out from the fan, so I assume that the fan works. However, I notice that the fan does not exhaust anything (ex. Steam after shower). What could be wrong with the fan? Is there anyway I could fix it? Thank you.

Either the duct from the fan to the outside is blocked, or the backdraft preventer is not opening. This is a flap usually right at the fan.

The exhaust duct work needs to be inspected.

If you hear a sound that doesn't mean the fan is working. See if you can see the blades turning, you might have to pull the front cover down or take the cover off. If the fan isn't turning you probably need a new motor and if it is turning then look for an obstruction in the venting system. Most likely the vents are in your attic or between your ceiling and the floor above. Also there is a butterfly valve to stop air from blowing from the outside into your bathroom, make sure that is working properly. It is located between the fan blades and the exhaust vent. Sometimes there is another butterfly valve at the end of the vent on the outside of your house. Good luck