Quite often they are the same: you can start or begin your meal, the day, a job etc. Begin can sound a little more formal even if the meaning is the same: "We will begin the meeting with a vote of thanks" or "Don't start talking again! I'm trying to work."
You can use start in most situations. However, there are some cases where begin is not possible. These include:
"start working" eg "My computer won't start." You can't use begin to talk about a machine functioning.
"make something start" eg "How do you start this car?"
"start a journey" "Let's start early before the traffic builds up."
On the other hand, someone learning a new subject is a beginner, not a starter.
Otherwise the two words are mostly the same, and grammatically can be used in the same way.
You can use start in most situations. However, there are some cases where begin is not possible. These include:
"start working" eg "My computer won't start." You can't use begin to talk about a machine functioning.
"make something start" eg "How do you start this car?"
"start a journey" "Let's start early before the traffic builds up."
On the other hand, someone learning a new subject is a beginner, not a starter.
Otherwise the two words are mostly the same, and grammatically can be used in the same way.