Learn Portuguese (Portugal): Está lá? Quem fala?

Literally, Está lá? translates to "Is [someone] there?". In Portugal, this is the standard and most traditional way to say "hello" when answering the telephone. You will also frequently hear people say Estou, Estou sim, or Está lá, sim? when picking up.

Can I use Está lá to say hello to someone in person?

No, Está lá is exclusively used for answering phone calls, radio communications, or checking a connection (like testing a microphone). If you are greeting someone face-to-face, you should use standard greetings like Olá, Bom dia, or Boa tarde.

Why use the third-person Está instead of the informal "you" form Estás?

When you answer the phone, you usually do not know who is calling yet. Using the third-person conjugation (Está) is the safest choice because it works as a polite, formal greeting matching the você form, or simply as an impersonal way to ask "Is anyone there?".

Why use fala (speaks) instead of the continuous tense for "is speaking"?

While European Portuguese does have a continuous structure (like está a falar for "is speaking"), it is completely normal to use the simple present tense like fala for actions happening in the moment. Quem fala? is simply the set, natural phrase for asking "Who is calling?" or "Who is speaking?" on the phone.