Try holding down CMD-R when booting, it might take awhile, but should put you into recovery mode. Try to re-install High Sierra from there if you can.
If you had some anomaly during the time before you last shut down. (such as, a forced shutdown, during an APFS conversion, or Filevault 2 encryption) You may have corrupted critical files.
The status you are describing, means that a bootable drive is present. It could mean your drive is broken, or just the data is messed up. The quickest easiest thing to do, would be to re-install High Sierra. If you did in fact force shut down during a critical process like those mentioned above, it is best to format with Disk Utility before re-installing. (With that you might have an issue with the current set of betas, as it does not seem that you have the "expert" skills to work around any issues that may arise.) The only reason I assume you lack the "expert" skills for that process, is because you are here, in the wrong place, asking for help.
