Shut is another word for closed. The window in the picture is shut.
A shutter is a device found inside a camera that lets light through for a short time. The longer the shutter is open, the more exposed the resulting photograph is. You need to have the shutter open longer when there isn't much light.
You are shy if you are feeling nervous or uncomfortable when you are with other people. A shy person may want to stay quiet or not speak first. People are often shy when they are new to a place, or when meeting strangers.
A sickle is a cutting tool with a curved blade that used to be used to harvest grain by hand. Sickles are still used in some developing countries but in developed countries they have been largely superseded by mechanical harvesters.
