Answer:
when an electric current flows through a conductor such as a metal wire, the moving electrons can collide with the ions in the metal. This makes it more difficult for the current to flow, and causes resistance.
The resistance of a long wire is greater than the resistance of a short wire because electrons collide with ions more often.
The resistance of a thin wire is greater than the resistance of a thick wire because a thin wire has fewer electrons to carry the current.
Hope this clarifies your doubt.