CNPJ, short for Cadastro Nacional da Pessoa Jurídica, is an identification number of Brazilian companies issued by the Brazilian Ministry of Revenue, in Portuguese "Secretaria da Receita Federal" or "Ministério da Fazenda".
The terminology used in its name literally means "national juridical person registration" as opposed to the CPF number which is issued for individuals.
In the past CNPJ was named CGC, short for "Cadastro Geral de Contribuinte", in Portuguese it reads General Taxpayer Registration and is no longer used anymore.
The CNPJ has a total of 14 digits number formatted like this 00.000.000/0001-00. The first 8 numbers are the registration itself, the followed 4 numbers identifies the entity branch (0001 default for the headquarters) and the last 2 numbers are the check digits.