About this character
U+2764 HEAVY BLACK HEART entered the standard in Unicode 1.1 (1993) as part of the Dingbats block, a wholesale incorporation of Hermann Zapf's ITC Zapf Dingbats font from 1978. The name carries the typesetter's nomenclature: "heavy" because the glyph is a solid weight in Zapf's design — a heavier sibling to the open hearts in Miscellaneous Symbols like U+2661 WHITE HEART SUIT and U+2665 ♥ BLACK HEART SUIT (the playing-card pip).
The character has no HTML named entity. The familiar ♥ resolves to U+2665 ♥ BLACK HEART SUIT, not to U+2764. This is a frequent source of confusion: the named entity is older than U+2764 itself in the HTML 4 spec. To produce the heavy heart in HTML you need ❤ or ❤, or simply paste the glyph in a UTF-8 document.
U+2764 is also the base codepoint for the most common red heart emoji. The standalone codepoint has a text presentation default, which means many fonts render it as a black or single-colour glyph. To request the colour emoji presentation, follow it with U+FE0F (variation selector-16): ❤️ is the two-codepoint sequence 2764 FE0F. Skin-tone and colour variants extend the sequence further — the rainbow heart emoji is the four-codepoint sequence 2764 FE0F 200D 1F308, joining a red heart to U+1F308 RAINBOW with a Zero Width Joiner. See the emoji ZWJ sequences guide for the full mechanics.