Picture this real world scenario:

if it is raining {

    if the Internet is working {

        game

    } else {

        panic

    }

} else {

    go out and do something

}

Real decision tend to be more complicated than either one thing or another (if/else).  Here there is one initial decision based on rain.  If there is rain there is another decision so it is placed inside the "what to do if it is raining" place.  This is known as a nested if.  There is no limit to how many if statements you can put inside other if statements like this.  In JavaScript  you might be doing something based on user actions but the result might be different depending on time or what was clicked on.  There is no page to create for this but you will do nesting later so make sure you understand the concept - it is vital.  This is a simple if/else:

if (fred<1) {

} else {

}

This is the same one with another one nested:

if (fred<1) {
    if (green<1) {

    } else {

    }
} else {

}

and this adds a nested if inside the else:

if (fred<1) {
    if (green<1) {

    } else {

    }
} else {
    if (elephant<1) {

    } else {

    }
}

and finally another nested if inside the else of that:

if (fred<1) {
    if (green<1) {

    } else {

    }
} else {
    if (elephant<1) {

    } else {
        if (banana<1) {

        } else {

        }
    }
}