What is the purpose of typology in the Bible?

My question is for those who believe the Bible is the inpired word of God. I have been wondering what exactly the purpose of typology is in the Bible. The best answer I have thusfar is that it acts almost as a very long 'ruler' of sorts that enables the Bible student to acurately draw a very long but very straight line through the Bible 'connecting the dots' as it were, so that he/she may see the 'bigger picture'. Typology enlarges on themes that the Bible sometimes only gives limited details of at the time but later (some times only in the NT) elaborates on in more details. For example, the story of David and Goliath as a typology of the work that Christ came and did in our behalf as described by Paul in Rom. 5:18. By one act of disobedience Adam (king Saul) many were made sinners (all Israel remained as good as'defeated') until Christ (David) by one act of righteousness defeats Satan (Goliath) and because of His victory (David's) all men are made righteous (all Israel was victorious). Further: King Saul is mentioned as being 'head and shoulders higher than the rest' of the nation. So, he was like a 'giant' compared to the rest. He also stands as head (king) of Israel so too does Adam stand as head (king) of humanity. Goliath is described as wearing impregnable armour. So too does God describe Lucifer at the end of the book of Job (Leviathan). God says Leviathan is the king of the children of pride (How art thou fallen O Lucifer...) and that none but his (Lucifer's) maker can approach unto him (to destroy him). So too it is only Christ that could destroy Satan. David as symbol of Christ is quite lengthy so I will limit myself to the means he used against Goliath and the manner of his death. David destroys Goliath without sword or spear (not by might nor by power but by My Spirit) by throwing him with a stone against his head (bruising the serpent's head as promised in Gen 3) There is so much more but I hope you can see how many 'lines' start intersecting in just this one typology. In my mind typology used to be simply something beautiful that reminds me of the 'bigger picture' but the more I study them, the more they start looking like an elegantly detailed unification and harmonization of 'other things' I read of in various places in the Bible. Almost like a mosaic but each little tile in the mosaic is sometimes a mosaic in itself. I suppose that is why the humble romanesco broccoli will always be a tangible illustration to me of the principle behind typology - a small piece of it looks similar to the whole plant (aka self similarity, fractals, etc) Typology is very important to me but I am looking for a more concise answer as to it's purpose (why it is in the Bible). I am not that good with words (hence the long writing just to make a 'simple' illustration and explanation of what I mean so I can get to the point where I can try and make a simple statement as to its purpose). Anyone with wisdom to express this so simply so even a 'child' could understand? Thanks in advance. (And for all your time in reading all of this!