Difference between AGAMA SHASTRAS and NIGAMA SHASTRAS

According to me Nigam Shastra means Vedic system ...Nigam - (the Vedic system) - The guide
for Vedic Upasana (Nigam) is Karmakanda;which concentrates mainly on Japa, Jaga and Yagnya (fire sacrifice).

***Dharmashastras prescribe three main streams for the puja of Hindu Devatas, those are - Nigam,Agam and Lokacar. Nigam is the pure Vedic system, Agam is the tantric system and Lokacar,is the combination of both or some other system,which is followed with reference to the prevailing conditions of the locality, time and authorities.

***Agama Shastra means, in the Hindu context, "a traditional doctrine, or system which commands faith".
In Hinduism, the Agamas are a Non-Vedic collection of Sanskrit scriptures which are revered and followed by millions of Hindus. Their beginnings can be traced to the Indus Valley period of about 2500 BCE. The Agamas are the primary source and authority for yoga methods and instruction. The Shaiva Agamas revere the Ultimate Reality as Lord Shiva (Shaivism). The Vaishnava-Agamas (Pancharatra and Vaikhanasas Samhitas) adore the Ultimate Reality as Vishnu (Vaishnavism). The Shakta-Agamas (Tantras) venerate the Ultimate Reality as Shakti the consort of Shiva and Divine Mother of the universe (Shaktism). Each set of texts expands on the central theological and philosophical teachings of that denomination.Agamas are also sometimes known as Tantras.

The Agama traditions have been the source of early Yogic and Self Realization concepts in India. They have influenced thinkers and philosophers who sought an alternative to the excessive ritualism and sacrifices of the Vedic system of that time. Besides many non-vedic Hindu texts, early Jain and Buddhist scriptures are also called Agama texts.

Agama consists of four parts. The first part includes the philosophical and spiritual knowledge. The second part covers the yoga and the mental discipline. The third part specifies rules for the construction of temples and for sculpting and carving the figures of deities for worship in the temples. The fourth part of the Agamas includes rules pertaining to the observances of religious rites, rituals, and festivals