I want to know how clouds are charged and how they hold charge? Do clouds hold only one type of charge or both type of charge?
The charges in clouds sit on the tiny water droplets they are made of. The usual explanation for the charging of these water droplets and thus clouds is charge separation in convective air currents carrying these droplets. Clouds, like air, are normally not conductors they are insulating. Air, however, can become conductive by impact ionization at very high electric fields which can arise by the charge separation due to the moving water droplets. Clouds seem to be able to sustain negative and positive charges as probably everybody has witnessed when a lightning discharge occurs between two different clouds.