This is the 16012th most frequent Polish word.
trza
"Trza" is an informal, colloquial variation of "trzeba," meaning "it is necessary" or "one must" in English.
'Trza' is used colloquially here as a format for 'trzeba', indicating necessity or obligation.
Trza iść do sklepu.
One must go to the store.
'Trza' replaces 'trzeba' to signify the necessity to complete homework.
Trza zrobić zadanie domowe.
One must do the homework.
'Trza' serves as a colloquial shorthand for 'trzeba', again displaying a need to perform an action.