I dont know why i havent posted this earlier but i have been using Zygor for more then 2 years now and i simply love it! Worth every penny i paid for it. Speeds up leveling process and makes it pain free. And when your max level fun is not over and Zygor will help you every step of the way whether its Reputation grind, daily quests or achievements its brilliant.
Some addons are standalone, and are able to run without any additional addons being installed; others can require certain other addons to be installed to work at all, or integrate with other addons to provide additional functionality. Collections of addons that have been put together to form a coherent user interface are sometimes referred to as UIs.
Since it's like a premium version and it's not modifying game files it gets by somehow. I personally hate Zygor's guides and always have, it's just personal honestly. I understand some people like his guides and have no problem paying for them but I personally hate the idea of charging someone for an addon that - as this post points out - has plenty of bugs in it. These were fixed last week and if I'm paying cash for an addon I want that addon bug free and not causing a hassle and taking my time away when I could be doing a better job without an addon at all.
I only subscribed about 2 days ago after coming back to WoW after 6 years. The game has changed so much since I left right around the Cata release. I decided to start fresh on a new server. I still had all my old links and logins to places like Curse, WowInterface, etc. Loaded up all the addons I had favorited years ago (of the maybe 1/3rd that were still maintained). Got to level 20 in a few hours of playing. Had to look a bunch of stuff up.