A gear’s “pitch” tells the size of its teeth. It measures the distance from a point on one tooth to the corresponding point on the next tooth. The higher the pitch number the smaller the teeth can be expected. 32 pitch is for cars with very high horse power (such as gas powered car or 1:8); 48 pitch is popular for 1:10 offroad; and 64 pitch is mostly for 1:10 EP onroad.
When you divide the pitch (in millimeters) by its number of teeth you can get the module size of a gear. This is just a unit of size for indicating how big or small a gear is.
Tamiya always uses module size as measurement unit for representation purpose. 0.6-mod gears are “metric 48” and are actually 42.3 pitch while “metric 64” gears are 0.4 mod and are actually 63.5 pitch.
This third party web page provides the best possible technical explanation:
https://khkgears.net/new/gear_knowledge/abcs_of_gears-b/basic_gear_terminology_calculation.html
