Good evening my friends, thank you for granting me your attention on this bitterly cold night!

My question - my *meta*-question as the case may be - concerns the purpose of these words referred to as "tags". Let me be clear: I **use** tags. The site supports them, so why shouldn't I? But my understanding of their *reason for existing* is tragically incomplete. 

Are they used for searching? Are they useful in any *other* way? Or do they merely act as decoration, adorning these questions like so many baubles on a department store Christmas tree...

Please, let me know!