The difference between kharif, rabi and zaid crops are:
Kharif crops are sown during the monsoons. These crops are harvested at the end of the monsoon season. Paddy, rice, sugarcane, cotton, groundnut are the examples of kharif crops.
Rabi crops are sown during the winters. These crops are harvested by the end of either March or April. Mustard, wheat, gram, pea, almond are the examples of rabi crops.
Zaid crops are twice a year. It is grown during the summer and in between the rabi and kharif crop seasons. Cucumber and watermelon are the examples of zaid crops.