A discriminating monopoly is a single entity that charges different prices for different consumers. Higher price will be charged for price inelastic consumer and vice versa.
Types of Price Discrimination
i) Personal: Different prices are charged for different individuals (for example the railways give tickets at concessional rate to the "senior citizens" for the same journey).
ii) Geographical: Different prices are charged at different places for the same product (for example, a book sold within India at a price is sold in a foreign country at lower price). On their, China drops its goods in Indian market. As a result, watch and toy industries closed down their business.
iii) On the basis of use: Different prices are charged according to the use of a product (for example lower rates are charged by Tamil Nadu Electricity Board for domestic .useof electricity and higher rates are charged for commercial and industrial use).

The classification of market according to competition is as follows:
a. Perfect competition: Large number of sellers selling homogeneous products.
b. Imperfect competition :
i Monopoly        : Single seller
ii Duopoly         :  Two sellers
iii Oligopoly      : A few sellers selling homogeneous or differentiated products.
iv Monopolistic : Large number of sellers Competition selling differentiated products.

(i) It is a market structure in which there is only one buyer of a good or service.
(ii) If there is only one customer for a certain good that customer has 'Monopsony' power in the market for that good.
(iii) Monopsony is analogous to monopoly. But monopoly has market power on the demand side rather than the supply side.

(i) In duopoly there are only two sellers.
(ii) Each seller is fully aware of his rival's motive and actions.
(iii) Both sellers may collude.
(iv) They may enter into cut-throat competition.
(v) There is no product differentiation.
(vi) They fix the price to get maximum profit.

Firm : A single production unit in an industry, producing a large or a small amount of the commodity. (eg) Hamam, Lux are 2 firms.
Industry : A group of firms producing the same product. (eg) soap industry.