Are rainstorm and thunderstorm the same?

Not the same thing; The former refers to the intensity of precipitation, while the latter refers to the nature of precipitation.

Heavy rain, generally more than 50 mm in 24 hours, or more than 30 mm in 12 hours.

Thunderstorm: Also known as thunderstorm. Shower phenomenon accompanied by lightning. Thunderstorms are the most frequent in summer in China, and generally thunderstorms come and go quickly, with great intensity and small scale.