<span>We was to be umble to this person, and umble to that; and to pull off our caps here, and to make bows there; and always to know our place, and abase ourselves before our betters.
</span>
A sonnet is a 14-line poem that rhymes in a pattern:
A - B - A - B - C - D - C - D - E - F - E - F - G - G
If the poem you're talking about meets these criteria, it is then classified as a sonnet.
Two things to keep in mind when you're deciding whether to use formal or informal English are the B) occasion and the audience.
Of course you are going to change the way you talk depending on whether you are speaking to your friends or to your teacher - usually with the teacher you are going to use more formal English.
Occasion is also important - you won't speak in the same manner at a party and a cocktail.
