The tonearm is a critical, difficult to make, part of a turntable. It must ensure that the cartridge can follow the complex warping and edge engagement grooves of the record in both horizontal and vertical directions.
There are basically two types of tonearms: radial and tangential.
The radial tonearm moves in a radius around a fixed point. That point is usually supported by two bearings (dual pivot), or with a needle bearing (UniPivot.) Radial scan always has an error angle. Therefore, it is absolutely neccesary to align to cartridge in the headshell.
A tangentiall tonearm exactly plays to groove of the records the way the record has been cut. So, there are no tracking errors. However, it is complicated to make such a tonearm, sometimes they seem to come from a good Mecano Box.
The marriage between the cartridge and tonearm is essential. A good combination has a resonance-frequency between 8 and 12 Herz. Important parameters hereby are the effective armmass, weight and compliance of the cartridge.
Overall it comes down that a cartridge having a low compliancy better fits in a heavier tonearm, and an cartridge having a high compliance fits better in a lighter tonearm.
We can precisely calculate the optimal combination.