a) a transformer converts from one voltage to another (transforms volts). In your case, you should get a 110V/240v (or 110v/230v) transformer. You plug the the 230v end to the Singapore outlet and the appliance end will plug to the 110v end.

b) watt is the power consumption which is approximately volts multiply by current. So if the appliance is rated as 1100W at 110V, the current it is drawing is 10 Amps. You should buy a transformer that is rated for both the volts and watts. For volts you should get one as close as possible although you can make do with either 230v or 240v. For watts, you should get one that is o equal to, or more than the power consumption or more. Using a transformer with a lower wattage rating than the appliance will cause overheating on the transformer and may result in an electrical fire.

c) going into the difference between volts and watts will be quite technical. One loose analogy is to use a river as an example. Volts will be the speed of the water in the river. Current is the volume (quantity of water) and Watts is the volume of water traveling per unit time (per second)

Other consideration.
In my opinion, it is not advisable to operate an appliance using a transformer unless you really have no choice. A transformer is heavy and a good quality one is expensive - especially for the hight wattage (1,000W and above)

If not use properly may cause damage to the appliance. If you really want to go this route, then ensure that the plug in your 110v appliance cannot be used in the local 230V socket and label it. If you plug the 110V appliance into the 230v socket directly, you will definitely damage your appliance.