Mixed farming refers to the practice of growing several crops and also rearing animals simultaneously on the same piece of land. This agricultural system allows farmers to diversify their income sources and reduce risks associated with relying on a single crop or livestock.

Option 1, which suggests that mixed farming involves growing several crops in a planned way, is not completely accurate. While mixed farming does involve growing multiple crops, the planning aspect is not explicitly mentioned.

Option 2, which states that mixed farming involves growing both Rabi and Kharif crops, is incorrect. Mixed farming is not limited to specific types of crops but includes a variety of crops.

Option 4, which suggests that mixed farming involves growing fruits and vegetables, is too specific. While growing fruits and vegetables can be a part of mixed farming, it also includes other types of crops and animal rearing.

Therefore, option 3 is the correct answer as it accurately describes the concept of mixed farming as the simultaneous cultivation of multiple crops along with raising animals.