There are regional differences of terms for canning and preserving. Like the whole bunch of recipes and specialities represent this is a sign of the variety. The terms for preserving and canning don't only indicate the procedure of conservation.
Preserving and canning is often used as a hypernym. The German word "einwecken" is even protected by trademark law. Preserving is known as a process where heat is needed to create a vacuum. For example the WECK preserving method, the normal preserving process or your butcher's preserved sausage – all of this works according to the same principle.
Pickling is a different conservation method. It's about laying fruits and vegetables into oil, vinegar or alcohol without using any external energy.
This is the classic form of preservation. The filled jars (WECK jars always have a rubber ring, glass lid and clamps while twist-off jars have a suitable cap) are put in a pot and closed. The top jar should be covered with water by three quarters. Then you heat up the water until it's boiling. Now the preservation process starts. After the required time (it differs from size to shape) extract the jars from the pot and let them cool down. But don't put them onto a cold surface! If they are cooled down, remove the clamps if there are any. If the lid is still closed tightly the process has been successful.
This process works like preserving in a pot, but the advantage is that the kettle disposes of its own heating unit. So you have your own temperature sensor and timer. Put the filled jars into the kettle and fill in the water. The water should have the same temperature as your filled jars. Now the temperature has to be adjusted. Older kettles can just be put onto the stove. Reaching the required temperature the duration of the process depends on the kind of food that is to be preserved.
The jars have to be stacked as usual in your pressure cooker. Fill in some water. Depending on the kind food you intend to preserve the ring has to be set on level 1 or 2. The preserving process starts now. When it ends take the pot off the stove. The pot has to open all by himself. Don't accelerate the process by interfering.
This methed is quite unusual, but on the other hand a steam cooker is very easy to use and efficient. Place the jars in the lowest grate of the steam cooker. It's very important that the jars don't touch each other. Otherwise the steam isn't able to reach every single jar. You can use the temperature and time indications of the recipe. Having turned off the steam cooker the jars should stay inside the cooker for about 30 to 60 minutes.
First of all you need a 2 cm (0.78 in) high pan. Fill it with hot water and place the jars in the pan. But the jars are not allowed to touch each other or the side parts of the oven. Set the top and bottom heat to 175°C. The jars stay in the pan until you discover little air bubbles inside the jar. If the food is made of fruits you can turn off the oven now. If it's made of vegetables or meat set the temperature to 150°C for 90 more minutes. Later you can turn off the oven, too.
This isn't really about preserving, but it's basically about jarring. This method is especially used for marmalades and jams. The fruits and their juice are cooked with the appropriate amount of sugar until they begin to jelly. The compound is filled into the jars that have to be shut tightly. Usually you use screw lids for twist-off jars. Partly some jars are closed with cellophane.
You need a temperature of 119°C to preserve milk products, but normally water just boils at 100°C. This means you need a pressure cooker. Otherwise the milk will turn sour. Nevertheless it's possible to preserve milk products in a normal way, but you have to keep them in the fridge after the preserving process. Thus the durability of the food will at least be extended.