Several parts combine into one character.

Traditional 驛: 馬 (horse) + 睪 (a phonetic component). The character originally meant "post station / relay station" — the rest stops along ancient Chinese and Korean imperial roads where messengers changed horses. As communications technology evolved (horse → train), the meaning evolved with it. Three forms: 繁體 驛 / 新字体 駅 / 简体 驿.

Critical CJK divergence: this is one of the clearest cases where the same character has different prominence in different modern languages. — Japanese: 駅 (eki) is the everyday word for "train station". You see this character everywhere in Japan — every JR or metro station signpost. 駅前 (ekimae, "in front of the station") is one of the most-used terms in Japanese addresses and real estate. — Korean: 驛 (yeok) survives in train station names like 서울驛 (Seoul Station) and the modern compound 驛勢圈 (yeoksegwon, "station-power-zone" = catchment area for property prices), but Korean otherwise uses the term 역 mostly via Hangul. — Mandarin: this character is largely obsolete. Modern Chinese says 站 (zhàn) for "station": 火车站 (huǒchēzhàn, train station), 地铁站 (dìtiězhàn, subway station). The traditional 驛站 (yìzhàn, post relay) survives only in historical contexts.

So for English-speaking learners: in Japan you must learn 駅; in mainland China you must learn 站; in Taiwan you'll see the traditional 站 too. Korean Hangul writers may not encounter the character itself often.

Japanese: on-reading エキ (eki) is dominant — 駅 (eki, station), 駅前 (ekimae, in front of station), 駅員 (ekiin, station staff), 駅長 (ekichō, stationmaster), 始発駅 (shihatsueki, origin station), 終点駅 (shūtenseki, terminal station). The character anchors the entire transportation vocabulary in modern Japan.

Memory aid: a horse (馬) waiting at a relay post — the original meaning, now applied to trains.

In Japan·駅 = train/subway station (everyday word)

In China·驿 = nearly extinct; modern Chinese uses 站 (zhàn) for "station"