There are two ways of telling something to somebody. A long one and a short one. You can easily measure the size of it by the pause that one takes after they say to you: 'I must tell you something...'. If it's going to be a good or neutral thing - they will tell you this immediately and the pause will be short. 'I must tell you something, I watched a great movie last night'. No pause at all. If it's something bad - the pause will be long. 'I must tell you something...' A few seconds go by and you ask 'Yeah? What's that?'. 'Well, it's not easy...' - the longer it takes them to get it out, the worse it's going to be. A cat doesn't go up to a mouse and say 'I must tell you something, I'm going to eat you alive now'. That's quite bad even without a pause and this is how humans' language differs from animals'.
Now think, how do we, as language-users, interpret what other language-users try to express? This is what pragmatics is concerned about but if we ask further and try to work out why we can also make sense of what we read in texts, understand what the authors mean, often despite what they literally say, and then eventually correspond with them and take part in a conversation, that is in fact when we realise that communication is a truly complex activity. Or, even on a simple level of every day communication - why do we presume one's a pessimist if they see a glass as half empty rather than half full?
We are very special creatures that can not only differentiate between correct and incorrect form/structure/spelling/pronunciation (most of us can anyway) but also we can cope with items such as headlines in magazines. 'Plane crash, 76 die' - we automatically know that there is a relation between the two phrases without elaborating. Furthermore, even if the text we see is grammatically incorrect we still often make sense out of it so our brain does not reject the messages with mistakes in it. To see what I mean, try talking to a foreigner who doesn't speak fluent English, or read their texts, and see how even despite their mistakes you will still, most of the time, understand perfectly what they mean.
Are you ready for some more fascinating facts? We instinctively know that a sentence must have a certain structure - and now don't worry about your spelling or grammar. Even though some of you would probably write: 'Your beautiful' rather than 'You're beautiful' I highly doubt any of you would say 'Are beautiful you'. Now, we also know that some rules about the structure are surrounding texts that are consisted of sentences. These depend on quite different factors that are describes in terms of cohesion (the ties and connections in text). For example: 'My boyfriend once gave me a beautiful ring. He did it because he loved me. That gift was very special to me. We sometimes argue. However, we love each other so we always make up' - There are connections present in the use of pronouns, which maintain reference to the same people or items throughout: boyfriend-he, ring - it, my-me etc, lexical connections: beautiful ring - that gift, and finally there is also a connector 'however' which marks the relationship of what follows to what went before. Additionally we see that first sentences are in the past and create connections with those events whereas two last sentences indicate a different time. Can you see now how fast your brain works and simply sucks all this information in? So this is exactly how analysis of these cohesive links gives us slight insight into how writers form what they want to express and, what's more important, gives us crucial factors in our judgment whether something is well written or not. (Imagine that in the given text we used different connections between the sentences but ones that are difficult to interpret, for example: 'My boyfriend once gave me a ring. The bike is yellow. However, we love each other so we always make up. He did it because he loved me').