For some people, saying b and p is difficult. For instance, if your mother tongue is Arabic, you will have difficulty saying the p.
Now, in English there is an additional feature that you need to use when you say words that start with a p.
The p is aspirated. Aspirated means there is air blowing out of your mouth when you say the p.
What you’re doing is actually make the p with your lips and then blow out a puff of air. It’s almost as if you’re saying p and then h.
With the b there is no aspiration. So no air flowing.
Now have a look at the following video to see how it works for other sounds. You can listen to examples, and then try yourself.
Watch it here.