They are used for the measurement of continuous current, although they can also be used in alternating current, but they do not isolate the circuit to be measured as do the current transformers.
The shunts generate a standard output voltage (usually 60mV) according to the intensity that flows through them.
The precision is indicated by the class, being the most used class 0.5 (0.5% error) and class 0.2 (0.2% error).
For values up to 50A they are usually used with an insulating base for fixing.