Announcing LAMBDAs to Production and Advanced Formula Environment, A Microsoft Garage Project

Im curious about where to save and store my custom formulas, 
under names is the stuff saved in name manager and under modules we have something else which i understand is something different but im not sure what the difference is and when to use what.

some kind of guide / tutorial would be welcome to me. 

Dev's: parameters in functions is a good step. but it would be nice if  input parameters could be set with requirements and error messages separately from then main functions. 
if a formula requires input arrays to be single column og single row array of equal length and there needs to be a check  if one array needs to be transposed or if some of the cells contains text, ISBLANK or something else it would be nice if there's checks could be done separately and for each error being able to set custom error messages. I understand for simple formulas it might not be needed. but for complex formulas that is going to be used by a group of people, it would help a great deal.