Most stories start at the beginning. That would make sense.
But sometimes you can mix it up a little and start from the middle or even the end. By doing this, you can skip a lot of set-up and exposition and get straight into the action of the plot. You can then drip feed the crucial beginning pieces through devices like flashbacks or recounts, or just leave the reader to work it out themselves!
This is often referred to as starting “in media res”, which is a fancy Lating phrase meaning “in the midst of things''. It is usually an exciting way to kick off a story, especially when there is an unusual or crucial situation the character finds themself in, and you are left wondering how they got there.