To navigate to the declaration of a symbol (variable, method, class, etc.) hold down the Ctrl key while hovering the mouse pointer over the symbol to turn it into a hyperlink, then click on the symbol to follow through to the declaration.
You can also press Ctrl+B while the cursor is positioned on the symbol, or choose Navigate | Declaration from the menus.
Hold the Cmd key and click to navigate to the declaration of a symbol. Press Cmd+B to navigate to the symbol declaration.