Answers for "what is a viewport"

viewport

<meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta name="description" content="A page's description, usually one or two sentences." />
    <meta name="keywords" content="banana, banana facts" />

css viewport

<meta name="viewport" content="width=device-width, initial-scale=0.9, user-scalable=no">

viewport

// viewport for Responsive Design
<meta name="viewport" content="width=device-width, initial-scale=1.0">

viewport

<!-- Responsive // Viewport -->
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=0">