prescriptive vs descriptive
The differences between prescriptive and descriptive involve one of the many common myths about linguists and about linguistics itself - and that is that linguists correct people's language and want everyone to speak "properly."
This is a fairly pervasive myth and it is false.
Linguists are desciptivists. This means that they observe and analyze language the way that it is used, not the way it is "supposed" to be used. Linguists are not interested in correcting your grammar - in fact, we find grammatical errors interesting, because it reveals the ways that language is processed and used.
Insisting that there is a way to properly use a language is what prescriptivists do. These rules are often based on the Standardized language and are taught in schools and colleges. However, Standardized language is often steeped with issues such as eliticism and racism, which discriminate against people with poorer backgrounds as well as people of color. An example of this is the use of African-American Vernacular English (AAVE), which is often said to be "ungrammatical." This is not true. AAVE has its own set of grammatical rules that do not follow "Standardized" English rules.
It is because of prescriptivism that English grammar rules have such things as "don't end sentences with prepositions" or "don't split an infinitive ("to boldly go")." These grammatical rules are actually from Latin and the people who wanted to put it in the English language did so because they wanted English to sound more sophisicated. In reality, these grammar rules have nothing to do with English grammatical structure. It is perfectly valid to end a sentence with a preposition and to split an infinitive. In fact, in Latin, it was actually impossible to split an infinitive because infinitives in Latin are one word, unlike in English where they are two words (to go, to run, to eat).
The fact is that everyone uses language differently and this is not a bad thing. In fact, this makes us unique and gives us greater insight into how the language works. P.S. We all have an accent!
Linguists don't judge your grammar, they analyze it.