Oven safe meat thermometers are meant to be inserted into meat before the meat is placed in an oven to cook.
They can be dial or digital.
The dial ones work by “bimetallic coil” action. Inside the shaft part of the thermometer, there is a metal coil that expands when heated, which makes the dial move. Where it reads the temperature on the skewer part is generally from the tip upwards to about 5 to 6 cm (2 to 2 1/2 inches). Though the temperature inside the meat along that length being measured may vary somewhat, what you see on the dial is an average of the range.
Some people prefer this type to instant read meat thermometers because they go in and stay in, negating the need to poke the meat any more than necessary in order not to let juices out (though one could always just poke an instant-read thermometer in in the same place each time.)
If you forget to put an oven-safe meat thermometer in at the start of cooking, and need to get the temperature, put it in, and wait at least two minutes to get a reading.
You can also get microwave oven safe ones. Some microwaves come now with a built-in probe.