anything; whatever; everything
Used as a noun or in expressions to mean 'any kind of thing', 'no matter what', or 'everything'. Often appears with particles like でも, も, or in phrases like 何でもない.
何でも好きなものを選んでいいよ。
You can choose anything you like.
彼は何でも知っている。
He knows everything.
Used at the beginning of a sentence to indicate that the following information is hearsay or something the speaker has heard. Often followed by そうだ or ということだ.
何でも、明日は雪が降るそうだ。
I hear it's going to snow tomorrow.
何でも、彼は来月引っ越すらしい。
Apparently, he's moving next month.
何でも is the plain word for 'anything', while 何でもかんでも is its emphatic, doubled form used to criticize excessive or indiscriminate behavior.
何でも means 'anything/whatever', while 何とも (similar in form) means 'not at all' or 'really/very' and is not interchangeable with it.