(2) Poetic language
Roman Jakobson, the Russian linguistic and critic, thinks in terms of language functions. Sometimes it may be just to establish friendly contact and it doesn't matter what we're talking about, so long as it is not liable to create conflict. Here the focus, the meaning, is personal interaction, creating a channel. Sometimes we way want primarily be to express emotions (focus on the person/people), other times to pass over information (focus on content of message). The poetic function is when the focus of attention is on the 'message' (i.e. the language) itself. For this reason poetic language is sometimes called 'reflexive'. This doesn't mean that in poems we don't also take account of other factors such as emotion and content.
Jakobson points out that the poetic function occurs in all areas of life not just in poems. 'Heinz meanz beanz', 'Go to work on an egg', 'No pain no gain', 'credit crunch' and so on are all examples.
A poem is a kind of text in which language itself is the defining feature. On this line of thinking all the poetic 'devices' we come across are seen as ways of turning our attention to the text as text. So poetry is not just understanding what the writer is talking about and how they feeling about it, but about language as such.
Jakobson's view tends to present poetic language as a sort of 'play', where we enjoy and celebrate the words in our mouths, as it were. Obviously there are more serious things here, such as having a sense of what human communication is, how language and thought intermesh.