Components of the game window

The official EL website has a nice overview of the interface.
The different components and their uses are discussed below.

Toolbar

At the bottom of the game window you have a tool-bar with buttons for shortcuts to frequently used tools. Most of these are also accessible through shortcut keys.

Status bars

Above the Tool-bar you have a status bar, showing your ethereal points (mana, blue), food level (yellow), health points (red) and carry capacity (emu, brown). To the right of these items you can have up to four (five?) skill bars. The first bar can be selected by clicking on the skill (left mouse button). Additional bars can be selected by using shift+left-mouse-button.