Grammar shows us which direction we are going in.
Consider the following sentences...
"Is this text a question?"
Let's consider things... now because the verb ("is") comes before the subject ("sentence") - and there are no irregular adverbs - we know that it's a question.
That's English grammar.
"By contrast, this text is a statement."
We know that's a statement because the subject ("text") comes before the verb ("is").
That's English grammar.
"Now consider the sequence of words in this text."
That sentence doesn't have a subject. Consequently, we know it's an "imperative", a command.
That's English grammar.
Grammar shows us these connections of the language. It shows us how we should connect parts of the language to other parts of the language. Consequently, learning the foundations of English grammar improves your accuracy and improve how clear you will be in your communication.
See below for my most recent blog posts about grammar and how learning grammar well can help with your English language learning.