I've been given an Amazon Fire Stick for xmas, I already have a smart tv and a Netflix subscription, so what is the point of the Firestick? I don't understand. Is it for Kodi? Does Kodi allow me to watch almost anything? Will I be arrested for using Kodi?? Is it illegal? I feel old.
The Firestick may give you some channels you don't currently have such as Amazon video. It also allows you to play some games such as Sonic the Hedgehog 2. It may be, of course, that the person who gave it to you didn't realise that it doesn't really add anything to what you've got already.
You can install Kodi on a Firestick. Use of Kodi is not illegal. It will not, of itself, allow you to watch almost anything. However, add-ons and plug-ins are available that allow you to watch, free of charge, content that you would normally have to pay for. It may be illegal to install these add-ons and plug-ins. It is almost certainly illegal to use these add-ons and plug-ins to avoid paying to watch content.
If the Firestick you have been given already has Kodi installed the giver may well have purchased it from someone who pre-loaded with add-ons and plug-ins. Pre-loaded Firesticks are readily available through ebay and other sources. The giver may have believed that it gives you free access to everything (which is essentially how these Firesticks are advertised) and not considered the legal issues. If that is the case you can safely use Kodi to watch free content and content for which you pay a subscription - you may find it better than other ways of watching this content. You should, however, avoid using it for watching non-free content without paying.
Kodi is a free piece of software, it's open source meaning no single company of person owns it. Anyone can use it on any device it is compatible with, it is not illegal and you won't be arrested for using it.