〜によると／によれば
According to (a source)machine translation
FormationNoun (information source) + によると／によれば; the sentence usually ends with そうだ／らしい
Noun + によると gives the SOURCE of a piece of information: "according to the weather forecast," "according to the news," "according to my friend." Since the whole sentence is relayed information, it almost always ends with a hearsay marker: そうだ or らしい — 天気予報によると、明日は雪が降るそうです. Without that ending, the sentence sounds as if it were left hanging, unfinished.
によれば means exactly the same but leans written and is slightly more formal; the two forms are freely interchangeable. When the source is what someone said, add 話: 友達の話によると (according to what my friend said).
Don't confuse it with によって: によって carries the meanings "by, because of, by means of, depending on" and does not cite an information source — 人によって違う (it differs depending on the person). To state something widely believed to be true without naming a specific source, Japanese uses と言われている ("it is said that").
Examples
天気予報によると、明日は雪が降るそうです。
According to the weather forecast, it will snow tomorrow.
ニュースによれば、この夏はとても暑くなるらしいです。
According to the news, it seems this summer will be very hot.
友達の話によると、あの店のラーメンはとてもおいしいそうです。
According to what my friend said, the ramen at that restaurant is very good.