Language systems and skills and Treatment of errors. 
Language systems and skills.
They are a set of skills that a person acquires, to be able to understand and express information in a language.
The four most important skills are listening, speaking, reading and writing, which are acquired with the passage of time and the degree of relationship with the language.
Listen: Consists of understanding what other people are talking about, it is the first skill that a person acquires, it involves the ears as well as the brain and serves to develop auditory comprehension.
Speak: Consists of emitting sounds to form words and that when these are agreed in sentences make sense to other people and understand what we are saying in that language, involves the vocal tract and the brain and serves to develop oral expression.
Read: Consists of interpreting symbols and written signs to encode a message that can be instructions, news or any other type of information, involves the eyes and the brain, it develops reading comprehension.
Write: Consists of producing a text by means of symbols and written signs to express information in a certain language, involves the hands and the brain, helps to develop written expression.
Treatment of errors.
An error can occur in writing, reading or speaking, because it is impossible to know perfectly all the rules of a language, whether they are grammatical, cultural or pronunciation rules. Mistakes are common when dealing with a language we are learning.
Mistakes must be corrected in order to learn from them, it is important to know what is wrong to avoid repeating it again.
To fix a mistake, you can ask another native speaker for help, research the rules of the language or use a digital translator to learn the correct way to write something.
If a person made a mistake and you know the language better, you can correct him, but in such a way that he understands what he made a mistake and without making him feel bad, so that he is not discouraged to continue learning.