OK, and LDR is a light dependant resistor. It works by lowing the resistance when more light is placed above the sensor, and the resistance increases when it is darker. A thermistor does the same, but with temperature rather than light. The acronyms NTC and PTC define what type of thermistor you have. NTC stands for negative temperature coefficient, and means that the resistance decreases with a higher temperature. PTC (positive temperature coefficient) means that the resistance will increase with higher temperatures.
These can all be described as transducers. A transducer is any device that changes one form of energy into another, usually to monitor or measure it. A thermistor is a thermoelectric transducer (heat changes to electrical energy), and an LDR is an electromagnetic transducer. There are all sorts of different types of sensors and measuring equipment that have transducers in them, such as Geiger counters (radioactivity into electrical) and motors (electrical to kinetic).
Depending on how deep you need to go into the different components, and whether you just need to know what they do, or the complications of how they work will change where to look for information. GCSE textbooks can be useful for simple to understand information about what they do and some basics on how they work. Electronics encyclopaedias contain detailed information on how they work, operating ranges etc.
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