At 4 years old a child can talk pretty good and by 4 years old the child should know between 1,500–1,600 words and be able to speak those words pretty good.
Once the child reaches 5 years old they learn even more words and should know between 2,100- and 2,200 words and should speak those words much better than when they were 4 years old.
Even at 3 years old the 3 year old knows some words and can speak some words pretty good and by 3 years old they should know between 900 to 1,000 words.
Children learn and speak at different rates than other children so don't worry too much if your child is not speaking as much as other kids of the same age.
But you could get the child checked out by a speech therapist just in case if you want too.
The child will eventually learn to speak and then you may not be able to shut them up.
However some kids are shy and will not speak much if at all around strangers so your child may talk just fine at home but may not when in public, in school etc.