"BEGIN" and "START" can be used interchangeably, but there is a little difference between “to begin“ and “to start”.

1. “begin” or “start” to mean the same thing but “begin” is more formal than “start”.
Ex :
1. When did you begin learning English?
2. The meeting didn’t start until 9 p.m

2. Use “start” for machines and making something start.
ex - I started the washing machine an hour ago

3. “Start” is used to talk about creating a new business
ex - She started a new restaurant and it’s been going really well.