Salto vs. tacão
While both salto and tacão refer to the heel of a shoe, the main difference lies in regional usage. Salto is the standard term in Brazil and is also used in Portugal, especially regarding high heels. Tacão is primarily used in European Portuguese to refer to the physical block of the heel itself.
Salto
A2This word is used in both Brazilian and European Portuguese. In Brazil, salto is the universal word for any shoe heel. In Portugal, it is most commonly used to describe the height or style, such as in salto alto (high heels).
Ela não consegue caminhar bem com esse salto.
(She cannot walk well with that heel.)
Quebrei o salto do meu sapato na festa.
(I broke the heel of my shoe at the party.)
Prefiro sapatos de salto baixo para trabalhar.
(I prefer low-heeled shoes for work.)
Tacão
B1This term is specific to European Portuguese (Portugal). It refers to the physical supporting block of the heel attached to the sole. It is rarely used in Brazil in this context.
O sapateiro precisa de substituir o tacão das botas.
(The cobbler needs to replace the heel of the boots.)
Este sapato tem um tacão de borracha muito resistente.
(This shoe has a very resistant rubber heel.)
O barulho do tacão no chão de madeira era irritante.
(The noise of the heel on the wooden floor was annoying.)
Summary
Use salto if you are speaking Brazilian Portuguese or referring generally to high heels in Portugal. Use tacão specifically when referring to the physical heel piece in European Portuguese.