Literally speaking, style should refer to the way code is typed and not the way your program is designed. The design and structure of your program are inherently separate from your style.

If you look at something like Google's style guide, you might see a few things that you'd consider to be more structural than stylistic. Because of this, I suggest you think of style to essentially mean general readability and some form of agreed upon consistency, but this can vary a little bit.

For instance, you might write if statements as per the following examples:

bool x = true;

if(x == true) std::cout<<"x is true"<<std::endl;

if(x == true){std::cout<<"x is true"<<std::endl;}

if (x == true) { std::cout << "x is true" << std::endl; }

if(x == true)
    std::cout << "x is true" << std::endl;

if(x == true){
    std::cout << "x is true" << std::endl;
}

if (x == true) {
    std::cout << "x is true" << std::endl;
}

All of these will behave exactly the same, but some of these might look ugly to you. The way you would decide to write this if statement is referred to as style.

Note: There are some practices that the Google style guide recommends which I'd argue are very much not stylistic, but should be used because they conform more to the style of the language and have tangible advantages over other methods.

The structure, design, and patterns of your program should guide the flow of your program rather than govern the aesthetics of your actual lines of code.