Camiseta vs. playera vs. remera
The words 'camiseta', 'playera', and 'remera' are Spanish terms which all refer to the English concept of a 'T-shirt'. However, the usage of these terms varies significantly based on the geographical region.
Camiseta
The term 'camiseta' is widely used throughout multiple Spanish-speaking countries, such as Spain, Colombia, Peru, and Chile. It is a universally recognized term for T-shirt amongst all Spanish speakers.
Me compré una camiseta de manga larga.
(I bought myself a long-sleeved T-shirt.)
Esta camiseta no tiene botones.
(This T-shirt doesn't have buttons.)
Su camiseta es de algodón.
(His T-shirt is made of cotton.)
Playera
'Playera' also means T-shirt, but this term is predominantly used in Mexico. It may not be understood in some other Spanish-speaking regions.
Mi playera favorita es azul.
(My favorite T-shirt is blue.)
Te vez muy bien con esa playera.
(You look very good with that T-shirt.)
La playera está un poco sucia.
(The T-shirt is a little dirty.)
Remera
'Remera' refers to a T-shirt in Argentina and Uruguay. This term might be unfamiliar to Spanish speakers from other regions.
Me regalaron una remera bonita.
(I was given a nice T-shirt.)
¿Dónde está mi remera verde?
(Where is my green T-shirt?)
Esa remera le queda grande.
(That T-shirt is big on him.)
Summary
`Camiseta`, `Playera`, and `Remera` all mean `T-shirt` in English. `Camiseta` is universally understood by all Spanish speakers, while `Playera` and `Remera` are regionalism used mostly in Mexico and Argentina/Uruguay respectively.