The basic language of LaTeX is broken up into environments and commands. Both begin with a backslash (\) and have required arguments (such as the text you want to modify or the name of the environment) in {curly braces} and optional arguments (such as the scale of a graphic are in [square braces]. (Not all commands have arguments, especially optional arguments. As you will see, the required argument of an environment is usually the name of the environment itself.)
Environments need to be opened and closed, because you will be putting a large block of text or other formatting inside the environment. You write tables in the tabular environment, put long quotes in the quote environment, put math in an equation environment and add images or figures inside a figure environment. (Actually, for short usage of math mode, you bracket text and commands with $dollar signs$, which is easier than beginning and ending a figure environment. Even the document itself should be packaged inside the document environment. Obviously, you can nest environments, but make sure you close them in a nested manner as well.
To begin an environment, write \begin{ environment name here }, then when you want it to end, write \end{ environment name here }, of course replacing "environment name here" with the name of the environment.
\begin{document} %the document environment is begun
\begin{quote} %starts a long quote using the quote environment
A trait that is associated with such an explosion of species is possibly a key innovation. A key innovation opens up or allows access to an ecological niche that enables the organism to take advantage of unused resources. Exploitation of new habitats can separate a previously cohesive population through migration and then further increase physical distance between the diverging populations. The new niche (in this case, different pollinators) can result in speciation.
\end{quote} %ends the quote environment ( note: before ending the document environment! )
\end{document} %the document environment is ended
Commands do not need to be closed, for they are just short instructions to LaTeX. You use commands to type special symbols like angstroms ( \AA gets Å) and tildes ( \~{n} gets Ñ). Commands are also used to force line breaks (\\), new pages ( \newpage), insert today's date ( \today) and make a title page using information previously defined. (More about the title page later.) A list of common special symbols are here, and you can find more about commands used in formatting here.
