This is the 1614th most frequent Polish word.
ludźmi
"People" (instrumental case of "ludzie").
The word 'ludźmi' is the instrumental plural form of 'ludzie', meaning 'people', used here as the object of 'z' (with) indicating the means or companionship in the action.
Rozmawiam z ludźmi o ważnych kwestiach.
I talk to people about important matters.
In this sentence, 'ludźmi' again serves as the instrumental plural form being used to express participation or association with 'z' (with).
Pracuję nad projektem z ludźmi z różnych krajów.
I am working on a project with people from different countries.
Here 'ludźmi' follows 'z' (with) to indicate collaboration, again utilizing the instrumental plural form to denote roles or participants in an action.