* {
    font-family: arial;
}

h2 {
    text-align: center;
}

/* select multiple elements by separating them with a comma*/
p, button {
    color: red;
}

/* selects all inside of descendent */
#outerDiv p {
    color: blue;
}

/* selects inside parent (direct descendant) */
#innerDiv > p {
    color: green;
}

/* selects all elements placed immediately after an element */
h3 + p {
    color:blue;
    text-decoration: underline;
}

/* selects all elements placed immediately before an element */
p ~ h4 {
    color: orangered;
}