Actually they are alike in some ways :

• The part of the balloon that holds the hot air or gas is called “envelope”.
• The basket that carries the pilot and passengers is the “gondola”.
• The pilots control their direction by taking advantage of different wind currents at different altitudes.

… in short, the main difference is the la content of th enveloppe : the first one uses hot air and the second helium (or hydrogen)

Gas balloons flights can last for days, unlike hot-air flights, which usually last about an hour.

What makes gas or hot-air balloons fly ?

Gas balloon ascends because the gas inside is less dense and lighter than the air on the outside of the balloon.

For a hot-air balloon, heating up regular air makes its molecules expand, becoming lighter than the surrounding atmosphere. That’s what causes hot-air balloon to lift off.