A microwave oven, or just a microwave, is an appliance that heats food using microwave radiation. The microwaves heat the water inside the food, so food cooks very fast in a microwave oven.
Microwave ovens cannot brown food like an ordinary oven can, and can't be used for cooking all kinds of food. Some microwaves are combination and also have some ordinary heating elements in them too.
A mortar and pestle are used together for grinding things down or mashing them into a paste. They are most often used for crushing or grinding herbs for cooking. The bowl-shaped part is the mortar, and the stick you use for grinding things is the pestle. Most mortar and pestles are made of stone, clay or heavy wood.
An oven is a container that is made very hot by fire or some other heat source. More modern ovens have a door that closes tight and a very evenly regulated temperature.
Ovens are used to cook food, most commonly baked goods like bread and pies and to roast meat or vegetables.
Plastic wrap, also known as Glad wrap, cling wrap, cling film, Saran wrap or Stretch-Tite, is a very thin film of plastic that comes on a roll. You use it to wrap up food to keep it fresh.
Some kinds of plastic wrap come on very large rolls and are used to wrap up large things like pallets of bricks or newspaper to stop them from being damaged in transit. These kinds of plastic wrap aren't meant to be used on food.