Why do these headings come out different sizes?

Question

With an underscore, you can make things in bold or italic.
Test
Test

You can also make headings without four hashtags and/or no hashtags at the end

See?

See?

See?

However the middle one is smaller.
Why is this?

Answer 1

The formatting is known as "Markdown". There are sometimes a couple different ways of doing each formatting.

You can use asterisks or underscores each side for italic/bold. You can use asterisks or dashes at the start of a line for a list.

Headers are made by different numbers of hashes at the beginning of the line, the ones at the end don't matter. There should be 5 levels of headings (1 to 5 hashes, see below). You can also put equals symbols under a line to make the large heading, and dashes for second heading:

heading 1
=========

heading 2
---------

Hash headings:

heading 1

heading 2

heading 3

heading 4

heading 5

Answer 2

This is just the coding of the site, not an error.
I don't know exactly what it's called. Markdown, I think.

**bold**

*italics*

<s>strikethrough</s>

##small header##

#big header#

big header
---

That's pretty much all I know.

Comments

We can do strikethrough?
Thanks!