The Emoticons block is, despite the modest name, the historical root of Unicode emoji. Located at U+1F600–U+1F64F on Plane 1 (the Supplementary Multilingual Plane), it contains 80 codepoints: yellow smiley faces, hand gestures, the three "see/hear/speak no evil" monkeys, and the now-iconic folded-hands gesture. When most people picture an "emoji," they are picturing something from this block.
About this block
Emoticons were added in Unicode 6.0, released in October 2010. The original additions — 76 faces and gestures — came directly from the Japanese mobile-carrier character sets developed in the late 1990s by NTT DoCoMo, KDDI, and SoftBank. When those carriers' picture characters became universally exchanged across operator boundaries by the late 2000s, the lack of a Unicode encoding for them was a serious interoperability problem. Apple and Google jointly submitted the proposal that brought several blocks' worth of emoji — Emoticons, Miscellaneous Symbols and Pictographs, Transport and Map Symbols, and Geometric Shapes Extended — into Unicode in a single release.
The block was extended later. Unicode 8.0 (2015) added U+1F642 SLIGHTLY SMILING FACE, U+1F643 UPSIDE-DOWN FACE, and the chunkier hugging face. Unicode 9.0 (2016) added U+1F644 FACE WITH ROLLING EYES. Unicode 10.0 (2017) brought U+1F92D FACE WITH HAND OVER MOUTH and several more — though those later "extended face" additions actually live in the Supplemental Symbols and Pictographs block at U+1F90C–U+1F93A rather than in Emoticons proper. The Emoticons block itself is now considered effectively full; new face emoji go to the supplemental blocks.
It is important to understand that the Emoticons block ≠ all emoji. The full emoji set spans many blocks: animals and food in Miscellaneous Symbols and Pictographs (U+1F300–U+1F5FF), vehicles in Transport and Map Symbols (U+1F680–U+1F6FF), modern additions in Supplemental Symbols and Pictographs (U+1F900–U+1F9FF), and Symbols and Pictographs Extended-A (U+1FA70–U+1FAFF). Heart symbols are mostly in Dingbats and Miscellaneous Symbols. Even ASCII-era marks like ☺ U+263A WHITE SMILING FACE — which long predates the Emoticons block — are technically emoji under the Unicode Emoji standard.
A handful of cultural specifics: the three monkeys at U+1F648 🙈, U+1F649 🙉, and U+1F64A 🙊 come from a 17th-century carving above the Tōshō-gū shrine at Nikkō in Japan, where the maxim "see no evil, hear no evil, speak no evil" (mizaru, kikazaru, iwazaru) is depicted by three monkeys covering their corresponding sense organs. The folded hands at U+1F64F 🙏 are officially named "PERSON WITH FOLDED HANDS" and were originally documented in Unicode as a gesture of prayer, supplication, or thanks — the popular reading as "high-five" is a recent reinterpretation outside the standard's intent.
Modern emoji rendering does much more than look up a single codepoint in this block. Skin-tone variation uses the Fitzpatrick modifiers from the Emoji Modifiers block (U+1F3FB–U+1F3FF); the family, profession, and combined-gesture sequences use the ZERO WIDTH JOINER (U+200D) and the VARIATION SELECTORS. The emoji ZWJ sequences guide walks through exactly how a single rendered emoji like 👨👩👧👦 is actually built from many codepoints.