When something starts, it begins to happen or exist. A start is also the beginning of something.
Starting something is usually good because it means something new is happening.
Examples:
The race starts in five minutes.
She always starts her day with a smile.
The cat starts to run when it sees the dog.
The baby starts to cry when it's hungry.
The party starts at seven, but I always start getting ready at six.
The movie starts with a big explosion.