Tried to erase content and now I am getting a white circle with a line through it

..sudz1:

..An instructional link of Support page(s) shows different 'partial startup screen' details..

and [includes This ⬇︎ One] among others.. Each, an information link; to workable solutions.

• If your Mac starts up to a circle with a line through it - Apple Support

https://support.apple.com/en-us/HT210901

"...A prohibitory symbol, which looks like a circle with a line or slash

through it, means that your startup disk contains a Mac operating

system, but it's not a version or build of macOS that your Mac can use..."

1. Press and hold the power button on your Mac for up to 10 seconds, until your Mac turns off.
2. Turn on your Mac and immediately press and hold both Command (⌘) and R to start up from macOS Recovery. 
3. While in macOS Recovery, use Disk Utility to repair your startup disk.
4. If Disk Utility found no errors or repaired all errors, reinstall macOS.
5. If you still need help, please contact Apple Support.

[..this, taken aside from: "If your Mac doesn't start up all the way" - Apple Support..]

~ with reference postscript: 'what to do before you sell, give away, or trade your Mac'

suzd1 Said:

"Tried to erase content and now I am getting a white circle with a line through it: Hello, I was trying to erase content to give my version of macbook 2010 to family member, now I have no idea what happened. I am stick with trying to reboot my macbook and keep getting the white circle with a line."

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Mount the Hard Drive in Disk Utility:

While booted into Recovery Mode [Hold Down: command + R keys upon boot], go to Disk Utility> tap the Hard Drive, then tap the Mount button. See if you can then install it. If it is already mounted, then unmount it and then remount it. See where you can go from there.