Why there is a line and sentence on my each post?

[M4TRIX04]

Hi, you guys,
Could you tell me Why there is a line and sentence on my each post? How to remove it or disable it.

[nozomizore1974]

This line and the words below mean you are using a list page rather than an article page.
So I guess your post file be named as "_index.md"?

[M4TRIX04]

Oh, Thank you, sir. Yes, my file name was _index.md. So if I create a single page like the about page, I should name the file "index.md".