from left to right the lights are Power - Hard Drive - Battery - Wireless
This is directly from the User Manual:
If the computer is connected to an electrical outlet, the Battery
light operates as follows:
- Solid green: The battery is charging.
- Flashing green: The battery is almost fully charged.
If the computer is running on a battery, the light operates as follows:
- Off: The battery is adequately charged (or the computer is turned off).
- Flashing orange: The battery charge is low.
- Solid orange: The battery charge is critically low.