Someone I was working with on Japanese remarked recently that he was slightly confused by my use of "grammar" in the plural: "grammars." He asked if I saw there being multiple structures within a language. I thought this would be a good topic to clarify.
All language has grammar. The word "grammar" is just a term used to describe the underlying structure that governs usage of the various parts and pieces of the language. For most people, "grammar" has terrible connotations, and people tend to associate the word with frustrating and difficult exercises rather than with the underlying form of the language. For this reason, I tend to use the word "structure."
The word "grammar" or "grammars" also refers to linguistic resources created to describe the structure of languages. Linguists have gone and observed how hundreds of languages work, and they have written down these rules and patterns in books which are known as "grammars." When I refer to "grammars" in the plural, I am referring to these resources. They are technical and intricate, but they are the most valuable resources you can have when learning a language. Why? Because they will give you all the underlying patterns of the language. Whether you like it or not, it is impossible to be fluent in a language without learning those patterns.
If you are going to have one resource when studying a foreign language, let it be a good linguistic grammar. After the Linguisticator video program, you should have enough of a foundation to understand the key linguistic concepts and terminology that will allow you to actually get the most out of these resources. You may have trouble finding good grammars, though. They're not "sexy" and don't sell well, so you can't always find them in bookstores or in public libraries.
Good grammars (the books) are gold mines, but it takes special training to see them as such. Most people shy away from these resources because of their technicality and complexity. It would, however, be better to spend your time learning to understand the content in a grammar of your new language rather than go through dozens of more superficial commercial resources. When you have gone and done the mapping of a language (phase II of the Linguisticator program), even those superficial resources become much more valuable because you will be able to see the patterns in them and their examples.