Herd and Heard are easily confused words. They are homophones, meaning they are sound the same, but are spelled differently.
The spell-check application of most word processing software programs would not catch a slip-up of these two words. Spell-check is looking for words that aren’t in its dictionary, and words that resemble words in its dictionary but are possibly spelled wrong. Spell-check isn’t perfect. It doesn’t know and can’t guess what word you wanted or what word you meant, it can only judge the words on the page. If you used words that are all spelled correctly, it gives you a pass anyway.
Autocorrect suggests words that start with the same letters. It suggests what word you may want to save time, but quite often, its suggestions couldn’t be more off base and produces humorous results.
Herd is a noun. It means a large group of grass-eating mammals that travel together. Herd is also in idioms like “follow the herd” and”heard mentality,” which both mean humans following the group. Following the herd means failing to act independently, using herd mentality means failing to think for oneself.
Heard is a verb, it’s the past tense of “hear.” To hear is to sense sound with your ears.
The following story uses both words correctly:
Hero was enjoying camping on the savanna until he felt the earth shaking underneath him. Then he heard a cacophony of loud, pounding sounds, and saw a dark blur headed his way. He leapt into a tree just before a herd of wildebeests thundered past.