How to figure out types of current sense amplifier?

To observe current waveform on oscilloscope, if I don’t have a dual channel DSO, I want to use an op amp to do this. Because there are even chips specifically designed to do this, it is called high side current sensing amplifier. And I just know it less, something like “High-side Amplifiers:
The current is measured between the supply rail and the load. The DC voltage applied on the input pins can be much higher than the power supply,” (source from Current Sense Amplifier Circuit Design), it has less words about it. So how do I figure out the high side or low side amplifiers?