What does "resale price maintenance" refer to in the context of agreements for selling goods or providing services?

Section 3 Anti-competitive agreements: (4) Any other agreement amongst enterprises or persons including but not restricted to agreement amongst enterprises or persons at different stages or levels of the production chain in different markets, in respect of production, supply, distribution, storage, sale or price of, or trade in goods or provision of services, including- (a) tie-in arrangement; (b) exclusive dealing agreement; (c) exclusive distribution agreement; (d) refusal to deal; (e) resale price maintenance, shall be an agreement in contravention of sub-section (1) if such agreement causes or is likely to cause an appreciable adverse effect on competition in India. Provided that nothing contained in this sub-section shall apply to an agreement entered into between an enterprise and an end consumer. Explanation.--For the purposes of this sub-section: (e) "resale price maintenance" includes, in case of any agreement to sell goods or provide services, any direct or indirect restriction that the prices to be charged on the resale by the purchaser shall be the prices stipulated by the seller unless it is clearly stated that prices lower than those prices may be charged.