Iqta in medieval India refers to the assignment of land revenue from different territorial units to army officers. This system was implemented as a way to compensate and support military personnel in exchange for their services in protecting the kingdom.

Option 1, which suggests that iqta was land assigned to religious personnel for spiritual purposes, is incorrect. While the assignment of land to religious personnel did happen in medieval India, it was known as "jagir" and not iqta.

Option 3, which states that iqta was charity for educational and cultural activities, is also incorrect. The iqta system was primarily focused on providing financial support to the army, not for charitable purposes.

Option 4, which suggests that iqta was the rights of the zamindar, is not correct either. The zamindar system existed alongside the iqta system, but they were distinct from each other. The rights of the zamindar referred to their status as local landowners and their collection of land revenue from peasants, while iqta referred specifically to the assignment of revenue to military officers.

Therefore, the correct answer is option 2, land revenue from different territorial units assigned to army officers.