Latex has two modes: equation mode and text mode. Notion's in-line and block equations are, of course, in equation mode by default. This means that you can insert math code such as \frac{2}{2} for $\frac{1}{2}$ or \lim\limits_{n\to\infty}f(x) for $\lim\limits_{n\to\infty}f(x)$ and it will render.
However, if you try to write text it will come out in italics and none of the spaces will render, for instance
$$ I just wrote some text here and it looks awful $$
You could manually insert spaces in math mode using a backslash \,
$$ but\ this\ is\ very\ annoying\ to\ do! $$
Instead, we can toggle text mode and we don't have to worry about spaces not showing up.
There are various ways to toggle text mode inside a LaTeX equation. The first is by putting your text inside a \text{} tag. For instance, the code on the left renders as the block on the right:
\text{This is some text}
$$ \text{This is some text} $$
Inside \text{}, you can no longer write equation code, but you can toggle back into equation mode either
\text{Text and }\frac{1}{2}\text{ is an equation}, or\text{Text and $\frac{1}{2}$ is an equation}These both render as
$\text{Text and $\frac{1}{2}$ is an equation}$
You can also go into text mode by using a specific font tag. For instance, if you write your text inside the brackets in \texttt{} you will get a monospaced typewriter font that looks like $\texttt{this}$.
Besides $\texttt{texttt}$, you can do $\textsf{textsf}$ and $\textbf{textbf}$.
These are the three font tags that will toggle text mode (i.e. spaces show up) and you can also put them inside a \text{} tag.
Then there are the math fonts, which you can only use in equation mode (i.e. you can't use them inside \text{} and you have to manually insert spaces with a backslash). These fonts are \mathfrak{}, \mathcal{}, \mathscr{}, and \mathbb{}. The last three only work for capital letters. Here's how they look:
$$ \mathfrak{This\ is\ mathfrak.}\\ \mathcal{THIS \ IS\ MATHCAL}\\ \mathscr{THIS \ IS \ MATHSCR}\\ \mathbb{THIS\ IS\ MATHBB} $$
Look at my code and notice I manually added the spaces between words with a \. The \\s in the code are just line breaks.