It is what is known as a "high level" in mastering a language. At this level, not only is one able to understand complex texts, but one can also infer and make deductions about what the text implies (if a text criticizes, advises, questions, or highlights a specific topic). You can produce well-structured and detailed texts with a wide range of vocabulary and linguistic cohesion. The speaker is able to use effective language in a large number of social, professional and academic contexts with ease. You can express yourself fluently with expressions and turns of phrase and make few errors. Its pronunciation does not make it difficult at all for the listener to understand the message.