At birth the Black Widow (aka Natasha Romanova) is given to the KGB, which grooms her to become its ultimate operative. When the U.S.S.R. breaks up, the government tries to kill her as the action moves to present-day New York, where she is a freelance operative.
Marvel is honestly the most guaranteed thing that I know of. I was a little skeptical about a movie randomly set in the already existing timeline that was not an origin story but they hit this one out of the park. Black Widow got her due. The new characters introduced were amazing and Yelena rocketed to the top of my MCU favorite characters. The action was amazing. There were a lot of great laughs. And the story explaining origins while at the same time moving characters forward was perfectly done. Possibly the most impressive part though is that the movie at the same time made it possible for more Black Widow movies if they want set in the past while bringing the surviving characters to current times too.
I would absolutely recommend people checking this out. It is an incredibly enjoyable summer blockbuster and I'm so glad to see Marvel movies back.