Second person, an undetermined person

Verbs

In Portuguese, as in English, we have three persons at the singular and others three at the plural: singular - eu, tu, ele/ela and plural – nós, vós, eles/elas. The funny thing here is that we don't normally use TU or VÓS as second persons in regular sentences. Those uses are too much formal and, in the coloquial Portuguese, they were substituted for VOCÊ and VOCÊS (just YOU in English), a historical contraction of the expression VOSSA MERCÊ*, which became VOSMICÊ and then, VOCÊ, as we use actually. The specific thing here is: we don't flex the verb at the second person as TU and VÓS, but at the third person as ELE/ELA and ELES/ELAS. Let's see an example, the verb QUERER (to want): The regular conjugation in the present will be: 

Eu quero (I want) 
Tu queres (You want) 
Ele/Ela quer (He/She wants) 
Nós queremos (We want) 
Vós quereis (You want) 
Eles/Elas querem (They want) 

In that case, in English, we use the same conjugation to every person, except to He/She. In Portuguese are six distinct conjugation, each one to each person. But, let's see a sentence: 
Do you want some cake? 
If we use the “official” second person, in Portuguese will be: 
Tu queres um pedaço de bolo? 
But, in almost all places we say: 
Você quer um pedaço de bolo?, applying the conjugation of the third person to the second. Why “almost”? Because, in Brazil, in some states as Rio Grande do Sul (border with Uruguai and Argentina) and Pará (border with the Amazon forest) the regular use will be TU and VÓS. It's part of the local culture and Portuguese spoken there. But, if you're not visiting one of those states, it's better the use of VOCÊ and VOCÊS or will sound a little weird. 
You got it?! Try yourself with other verbs. 
See ya! 

* This expression was used, at first, to kings, then, to nobility and now, to everybody. It's a true story of democratization of an expression. 