8. What are nationally determined contributions (NDC)?
In order to fulfill the main objective of the Paris Agreement, preventing the temperature from exceeding 2ºC from its pre-industrial level (1750), even better than not exceeding 1.5ºC, in its article 4, numeral 2, it is convenient to:
4-2 Each Party shall prepare, communicate and maintain successive nationally determined contributions that it intends to achieve. Parties shall pursue domestic mitigation measures, with the aim of achieving the objectives of such contributions.
4-3. Each Party’s successive nationally determined contribution will represent a progression beyond the Party’s then current nationally determined contribution and reflect its highest possible ambition, reflecting its common but differentiated responsibilities and respective capabilities, in the light of different national circumstances.
To see the other numerals of article 4 you can go to this PDF document, which also contains the entire text of the Paris Agreement.