A megabit is one million bits of computer data. A bit is the smallest piece of information a computer holds — a single yes-or-no, on-or-off. A million of those is a megabit, usually written Mb with a small b. This word matters most when you talk about SPEED, not storage. Internet plans are sold in megabits per second (Mbps): 100 Mbps, 300 Mbps, 1000 Mbps. Almost nobody says 'I have 100 megabits' out loud in daily life; they say '100 mega' or read the number off the plan. Engineers and salespeople use the full word. Note that companies like the megabit exactly because the number looks big: 100 Mbps sounds much faster than the same speed written as 12.5 megabytes per second, which is what you would actually see when a file downloads. Strictly, a megabit is 1,000,000 bits — the bit side of computing usually keeps the round decimal million, unlike the megabyte, which people often treat as 1,024 kilobytes.

百萬位元／兆位元（網速講的 Mbps 就是「每秒百萬位元」，台灣一般口語直接講「一百兆」「三百兆」）