The importance of grammar in language learning is often played down in language courses and by people who blog about language learning. They claim that you can learn a language either without actively studying the grammar (whatever they mean by the word), or that you only need to glance at grammar books and explanations now and then. This is partly a reaction against the grammar-translation approach to language teaching in which you concentrate on learning verb conjugations, noun declensions, etc, and on translating from and to the target language.
I think that grammar, i.e. how a language works, and grammatical terminology (if you don’t already know it), can be short cuts to achieving competence in a language. If you spend all you time learning nouns, for example, and don’t know how to put them together with other words to make sentences, then your ability to communicate will be very limited. Grammar provides the framework of a language and vocabulary provides the content. You need to learn both.
The question for me is not whether you need to learn/acquire grammar, but how you do so. Some people are able to read a grammar book, absorb the information and apply it – one friend, for example, spent nine months learning Finnish grammar, then moved to Finland (from Germany) and became fluent in Finnish within a few months. For most people though this is probably wouldn’t work. You can absorb a lot of grammar from extensive listening and reading, with some checking of grammar books, but some overt study can be useful as well.
What is your approach?