Both many and much are quantifiers. Many is used with countable nouns to show a large number. Much, on the other hand, is used with uncountable nouns to show a large quantity.
In English, countable nouns take the plural form, while uncountable nouns don’t. Study the following info-graphic to get more details about these two mostly confused expressions.
Basic notes to remember about the quantifiers many and much
Quantifiers (many and much) are used to specify quantities and numbers. Much indicates a large quantity, while many indicates a large number.