These are things I’ve seen or done, though of other input there may be a sliver.
Though I claim to know these things, your experience may differ.

Gasses:

• vary in volume
• vary in shape
• expand to fill their containers
• flow along paths of least resistance to points of least pressure
• are easy to compress

Air:

• consist of various gases
• has no definite shape
• has no definite volume
• has mass
• has weight
• creates pressure

Vapor:

• is gas below its critical temperature, the temperature at which it can become liquid by compression alone