When to use 2nd plural in Spanish?

Tu and Ustedes

Isto simplifica mucho porque no se usan los verbos en la segunda persona plural, ya que con ustedes se emplean los verbos de la tercera personal plural, los de ellos, ellas. Los latinos no conocen amais amad sois habeis cantais cantad....

Isto

Me equivoqué, tenia que escribir esto en lugar de isto, sorry :-)

We are talking about 'Voseo'
watch this url:
http://en.wikipedia.org/wiki/Voseo

Countries that feature voseo.
Dark blue: countries that use vos as the primary spoken and written form.
Medium blue: countries where voseo is predominant, yet not as intensive as in Rioplatense.
Green: Voseo as regionalism.
Light blue: Countries where the presence of voseo is proportionally small.
Red: Voseo practically inexistent.

Voseo is used in many spanish countries but not in all.

Anyway there's no problem at all, we understand each other perfectly.

in Costa Rica, and Honduras the most common informal pronoun is Usted, that is Usted can be used when addressing parents, children, lovers, friends, this is also true of many parts of Columbia, tu disappeared, vos is considered too informal and from this the use of Ustedeo rose, like you in English and você in Brazil, it can be both informal and formal, so in Central America and Colombia, you can do fine with only Usted and Ustedes, no strange looks raised...

Andalusian is NOT a dialect. It's a variety of standard Spanish-

Andalusian is a ugly variety, it sounds like latin american varieties most of the time

Andalusian is a dialect, and a fucking ugly one. Did you ever heard a person from Cadiz or Seville pronouncing S like Z? If you consider that to be standard Spanish then you have no idea of what a standard is. I can't conceive a person speaking that way on TV . Well, maybe in Canal Sur ...