And whats with the button bars on the right side (with horse icon) and in the lower left corner (with the green, yellow, red spikes and the potions or flasks)?
Lotro comes with 6 quickslot bars (= 72 slots total). 5 of them you can move around freely on your UI. 1 of them is unmovable (can only be moved via skinning).
You can control the bars from the Main Options while playing. There's a section for hotkeys. Also to move things around you need to "unlock" your UI.