What is a Space Character?
A space character ( ) is a character of text typed by pressing the spacebar that simply adds an empty space to a line of text. It doesn't have a glyph that gets drawn in its place like other characters have.
In real life, when we write words on paper, we separate words by "adding" spaces between them. Of course we can't actually "add" a space. We simply move the pencil or pen a bit to the right before starting a new word. There will be arbitrary amount of space between one word and the other, because we're human, not machine.
On a computer, this concept must be represented somehow, so instead of an "arbitrary" amount of spacing, we get a specific, fixed amount of space: one "space." One single space character. It doesn't matter if, when you handwrite, you put a few millimeters of space, or a few centimeters, everyone just presses the spacebar once to add one single space character between their words.
It's worth noting that this concept only makes sense in some languages. Japanese, Chinese, and Korean, for example, don't use spaces to separate their words in handwriting, so they don't have as much use for space characters in computers.