It may have changed since you did this lesson. When I heard it today, I heard the inflection for a question. Vocal inflections in another language are often hard to hear because they aren't the same as what we are used to. I still remember a time in Mexico when someone asked me a question, and I thought he was making a statement. It didn't sound like a question to me because the intonation was different than an English question.
Thank you for this simple and very helpful explanation since Duo's lessons didn't identify the root word 'falar' nor its correct conjugation. I'm just starting the Portuguese lessons and the module introducing falar was particularly frustrating because the practices didn't make it clear to me how to use 'fala/falo.' Checking a couple of external links didn't provide the information either - no mention of 'voce' in the lists of conjugations. As a raw beginner, sometimes I don't know enough to look for the right information or correctly interpret and apply what I'm seeing so my thanks to you Rae.F for this great help!
There is a pattern that all regular verbs follow. Not all verbs are regular, but most of them are. There are three mostly similar but slightly different patterns depending on whether the infinitive ends in -ar, -er, or -ir. And you do essentially just remove the infinitive suffix and add the appropriate conjugation suffix onto the root.
Don't worry about the bottom section for now, that's the simple past and Duo won't cover that for a little while.
The sequence of the conjugation list is standard: I, you (sing), he/she, we, you (pl), they. Or eu, tu, ele/ela, nós, vós, eles/elas.
Most Portuguese speakers, however, no longer use "tu" or "vós" and instead use "você" and "vocês", which grammatically speaking are treated identically to 3rd person. Hey, that's two verb conjugations you don't have to worry about!
There is no objective reason why it "should" be one way or the other. Different languages develop their own strategies for asking questions. Sometimes, just a change in the tone of voice is enough.
We do this as well in English, although it's a less formal register.
Statement: You are going [to a place].
Standard question: Where are you going?
Informal question: You're going where?