I first encountered this word in Egypt many years ago. As soon as someone does the slightest favour for you in some countries (eg "Is this the right platform for the train to Luxor?") their hand is out, insisting on some monetary return for the information they gave...even if it's, "I don't know." !!! (OK, slight exaggeration.)
In Western countries, the two words you need to understand are "tip" and "bribe".
I'm sure that another respondent will explain the difference. If not, I'll do that tomorrow.
Student or Learner