What is meta data and why is it important?
Meta data is used to help search engines find your content and rank it properly on search results. It is not as important as it used to be in regards to SEO, except for one aspect:
The search result preview - What you see when doing a search on Google.
You can basically control what you want Goggle to display in the search listing (marked in red above in the screenshot.) Above is an example of the article: 'Setting Up Ghost' that I wrote a while back.
Ghost has Meta Data built-in
So ghost has this nifty functionality built in, where you can add the meta data for each article you write and you can even add the meta data for tag sections.
What's nifty about it is that you can get a preview of how it will look like on Google. So basically changes you make can be seen instantly without waiting for google to crawl your site first.
I wasn't sure how it worked though, so I reached out to Ghost support and asked.
"CLARIFYING YOUR EXPLANATION
So Ghost IS taking the title of the post, along with the first 160 characters of the first paragraph and using it for the Meta Data EVEN if the meta data was not manually filled in?"Yes. That is correct. :)
After talking to the good Ghost folks i found out that the default behavior of meta data should be that the title and first 160 characters are being automatically grabbed by Ghost to feed the Google search result listing.
Don't always trust automation though...
So without filling in any meta data, Ghost will just grab the title and description automatically from the post and use for the meta data for search result and that means, theoretically, you don't have to really do anything.
However, I still strongly suggest you manually add the meta data because according to my own tests it seems safer and yields more accurate results.
Since Google plays a large role in how the search result will look like you garner more control filling in the meta data manually and not rely completely on Ghost to do it for you.
What do you mean?
Well, let's take a look at the Meta Data function
This is the Ghost admin panel preview, (without me filling in the meta data). Notice how the preview shows a nice listing. I basically thought that was the listing Google would use by default.
This is what actually showed up in Google, (without me filling in the meta data), and that is clearly wrong...
This is the Ghost admin panel preview, (AFTER filling in the meta data)
And this is what shows up in Google, (after I manually filled in the meta data.) As we can see that looks more accurate.
Notice how now the Google description matches exactly what I wrote in the Ghost admin panel meta data
Is this a the way it should be?
Well Ghost is trying it's best but Google has some say, in what will be listed, therefore, it is better to not rely completely on the default Ghost Meta Data feature and STILL fill in the meta data manually for each post
CONCLUSION
For now make sure to remember adding the meta data manually to increase the chance that your content will be found and clicked on by users searching on Google.
Refs
https://help.ghost.org/hc/en-us/articles/223237728-Post-Settings-Overview#add-meta-data
https://www.ghostforbeginners.com/adding-a-custom-meta-title-and-description