Is this referring to a social media, or is this referring to a person following another person physically?
No. Följa efter it to follow suit physically. Följa might be ambiguous as explained by rhblake above.
Just to be sure: Can it also mean understand sth/sb? As in "Are you following? Can you understand what I was saying just now?"
Shouldn't "You followed your sister" be correct? There's no "did" in this sentence. Is it implied or something? I've been getting really confused with some of these.
In English, you create questions by using do, but in Swedish, we create them by changing word order. In a normal sentence (i.e. in a main clause), the verb goes in second place. In questions, the verb goes first – the only thing that can go before the verb is a question word or a phrase that has the same function as a question word.
More details here: https://www.duolingo.com/comment/8970470
But if you added a question mark after "You followed your sister" making it "You followed your sister?", wouldn't that be correct, because the English version is still a question.
Yes, but there are two problems with this approach:
- We can do that in Swedish as well - turn a phrase into a question by changing the pitch at the end of it. So it'd translate better into Du följde din syster?
- The same logic applies to virtually every phrase in the English language, so it makes sense not to allow it in a language course, where we want to teach the more standard question construction - plus the extra labour it would require is immense.