It is important to use varieties and registers because here, we can learn how to communicate with other people who are conversational. In varieties there are STANDARD ENGLISH it is often used by Educated person like student like me, as I use standard English I can speak in front o many people reciting a speech. And in registers the way we use/used the language.
Language register is the level of formality with which you speak. Different situations and people call for different registers. This register is conversational in tone. It is the language used among and between friends. Words are general, rather than technical. This register may include more slang and colloquialisms.
The concept of register is typically concern with the way language varies when used in different situations for different purposes. Effectively, different situations and people call for different registers. The difference in word choice implies that when speaking in a formal situation we need to refrain from words considered non standard and informal.
Why is it important to use appropriate varieties and registers of language in a certain communication context? 