MacBook Air turns on but can't start up

Turn your Mac off and back on

Press and hold the power button on your Mac for up to 10 seconds, until your Mac turns off.* Then turn your Mac on again. 

• If your Mac doesn’t seem to be turning on at all, start with the steps for if your Mac doesn't turn on.
• If your Mac seems to be turning on but the screen is blank, continue to the steps below.

Start up from macOS Recovery

Try to start up from macOS Recovery, then follow the steps below.

If your Mac starts up from Recovery

1. While in Recovery, use Disk Utility to repair your Mac startup disk, then restart your Mac.
2. If your Mac continues to start up to a blank screen, start up from Recovery again, then reinstall macOSfrom Recovery.

If your Mac doesn’t start up from Recovery

• If you're using a Mac with Apple silicon or the Apple T2 Security Chip, you might need to revive or restore the firmware of your Mac.
• If you're using an external display instead of a built-in display, make sure that the issue isn't with your external display. 

If your Mac continues to start up to a blank screen, it might need service. Get service.

Our colleague @WheelieNick has offered some great guidance.

This pic you posted suggests to me that the laptop has some severe water (?) damage, so I'm not surprised that it is not booting properly.

Our colleague @WheelieNick has offered some great guidance. If their guidance provides no resolution to the problem, then this:

Get your Mac repaired and see how much will it cost: Mac Repair & Service - Apple Support 

You can make a Genius Bar appointment for hardware/software service and support using this link: Contact Apple Support - Apple Support

It also appears that this is an older laptop, 2010, 2012-ish model?

If so, then I would not spend any time or money trying to repair it. Put your resources toward replacing it.

If it is of that era, you can easily remove the internal drive and possibly recover the files that are on it to another Mac.