Like most markup languages, LaTeX collapses whitespace. This simply means that when it encounters multiple white spaces, it reduces it to a single one. This also means that it ignores a single return. An empty line between text, instead, starts a new paragraph.
These words are not that far apart. Neither are these But this is a new paragraph.

If you’re wondering why LaTeX does that, it’s because it regards multiple whitespaces and newlines as different from the single white space and return key, and requires different commands to produce them.
Reserved Characters
There are some preserved characters that make LaTeX do special things when you type them in the regular way. These are:
# $ % ^ & _ { } ~ \
That’s fine, but if you want to use them as a character in-text, you need to escape them. This can be done, in most cases, by adding a backslash in front:
\# \$ \% \^ \& \_ \{ \} \~
But, if you need an actual backslash, you can’t escape it with another backslash. For that, use the \textbackslash
command.
These are two dollar signs: \$\$ \par This is a math environment: $H_{2}O$

Built-In Strings
There are four commands that transform into a built-in string.
Command |
Visual |
Description |
|
December 20, 2015 |
Current date |
|
TeX |
What you’re learning (kind of) |
|
LaTeX |
What you’re actually learning |
|
LaTeX 2ε |
The current version |
Whitespace after Commands
Commands eat up all the white space right after it. To prevent this, add an empty required argument after it with empty braces. Alternatively, you can use the empty \<space>
command.
Isn't \LaTeX cool? Isn't \LaTeX{} cool? Yes \ \ \ it is!

Of course, commands that, by default, have a required argument, already display this behaviour.