Simple question about bolding

I am new to obsidian and generally new to Markdown so please take me with a grain of salt.

When bolding what will be a title, it is also bolding the line underneath. However, this does not actually ‘bold’ the text when in preview.

First step:
I am bolding the top line, but you see it puts the two ** of the markdown on the second line for some reason. You can also backspace them BACK onto the main line.

In this way, it causes the second line to be bold as well:
When you preview the file, the second line is not bold; but it appears bold when in document edit view.

I assumed selecting the top line of text and bolding, would only bold that line in the edit view. Am I doing this wrong?

Probably better to use this syntax for headings:

# Heading 
## Subheading
### Etc.

Markdown doesn’t like linebreaks, so the syntaxes you apply should stick to the same line. The ** on the second line doesn’t really know what you want it applied to, hence the oddities you’re experiencing.