Differences Between Formal/Slang
Hola mis amigos,
Maybe this is too broad of a question, but can someone please list some of the major differences between formal and slang Spanish? Gracias...
3 Answers
Formal: Señora, responder adecuadamente a su pregunta requeriría una amplia discusión de carácter academíco para llegar a una explicación que cubra satisfactoriamente la multiplicidad de usos entre los varios niveles de lenguaje, los diversos regionalismos, y la sutilezas de las variaciones relacionadas con la edad, el género, y el nivel cultural de los hablantes.
Slang: ¡Chama, qué loca! ¡Esa vaina está burda e' pelúa pa' responderla así nomás! Hay que echarle pierna y jarabe 'e lengua que jo... pa' hablar sobre todo lo que tiene que ver con eso. No, mejor ponte a ver la novelas ¡y pasa un buen rato sin estarte quemando tanto el coco!
Hi and welcome to the forum.
Every language has a certain vocabulary that is taught formally and accepted by most natives of the language. Slang would be words that are not considered part of the standard vocabulary of a language and that are used very informally in speech especially by a particular group of people.
It is a very broad question. It would be impossible to give a full description of Spanish slang here. Each country, in fact in every region of every country there are words that are understood and accepted by the people living there. There are also slang words used in most professions, sports, and even among teens. If there are particular words you are interested in, it would be best to be more specific. 
The formal or literary variety of a language is that level of a language which typically conforms to more prescribed syntactical constructions, often incorporates a more expansive vocabulary, and typically involves more complex sentences structures. This can be contrasted with the idea of "vernacular language" which describes more or less the actual manner in which people speak. This type of speech is also often referred to colloquial or informal speech.
Slang or argot, as alluded to by Nicole, is simply a word used to describe colloquial or formal speech which is generally only used or understood by a select group of people. Often these groupings are based on such factors as profession (i.e. medical jargon), socio-economic factors (i.e. street slang) or geography (i.e. southern slang). At its most basic, the term slang is simply a word (sometimes used pejoratively) to describe words and expressions that are difficult or impossible to understand by people who speak the same language but are outside of such groups.
In the Spanish speaking world, you will often find that the word "jerga" or "modismo" is applied to this type of language, and is often divided in terms of geographical location. That is to say that there are certain modismos (regionalismos) that are associated with various Spanish speaking countries or regions. For example, words and expressions specific to the country of Mexico might be referred to as "modismos de México" or simply "Mexicanismos" in that they, for the most part, would not be understood or at least not widely used outside of that country. Sometimes you will find that regional variations of the language will engender more specific naming such as with Lunfardo, a slang of socio-economic origins and specific to the city of Buenos Aires, Argentina.
If you are looking for specific examples, I have found the site "jergas de habla hispana" to be a good place to get started. Alternatively, you might type in "modismos de" or "jergas de" into the google search bar and investigate some of the suggestions.
