The correct answer is option 'A': First Schedule of the Indian Constitution.

Explanation:
The First Schedule of the Indian Constitution is a vital part of the Constitution as it lists the names of the states and specifies their territories. This schedule provides the details of the states and union territories that make up the political map of India.

Key Points:
1. Purpose: The First Schedule serves the purpose of defining the boundaries and territories of the Indian states. It helps in determining the jurisdiction and extent of each state's authority.

2. State Names: The First Schedule enlists the names of all the states in India, including Andhra Pradesh, Maharashtra, Tamil Nadu, Uttar Pradesh, etc. It includes a total of 28 states as per the current arrangement.

3. Union Territories: In addition to states, the First Schedule also mentions the union territories of India, such as Delhi, Puducherry, Chandigarh, and others. Currently, there are 8 union territories in India.

4. Detailed Information: The First Schedule provides detailed information about the territories of each state and union territory. It specifies the boundaries, areas, and other relevant details.

5. Amendments: Over the years, there have been amendments to the First Schedule, reflecting changes in the political and administrative divisions of India. For example, when new states were created or when certain territories were reorganized, the First Schedule was modified accordingly.

6. Representation in Parliament: The First Schedule is also significant in determining the representation of states in the Parliament. The number of seats allocated to each state in the Lok Sabha (the lower house of the Parliament) is based on the population and geographical area specified in this schedule.

In conclusion, the First Schedule of the Indian Constitution plays a crucial role in defining the states and union territories of India. It provides detailed information about their territories and serves as the basis for representation in the Parliament.