View source for Template:Tooltip/styles.css

.tooltip-display-text {
	position: relative;
}

.tooltip,
.tooltip-arrow {
	display: none;
	
	position: absolute;
	top: -.5rem;
	left: 0;
	
	transform: translate(50%, -100%);
}

.tooltip {
	width: max-content;
	padding: .35rem;

    background-color: var(--bg-color-light-x4);
    border: 1px solid var(--border-color-light-x2);
}

.tooltip-arrow {
	display: inline-block;
}

.tooltip-display-text:hover .tooltip,
.tooltip-arrow {
	display: inline-block;
}
Description	What you type	What you get
Italic	''Italic text''	Italic text
Bold	'''Bold text'''	Bold text
Bold & italic	'''''Bold & italic text'''''	*Bold & italic text*