Once a person learns to speak English well... i.e. they've practiced talking with friends and know how to manage themselves when shopping, taking care of their basic needs, then they might want to learn to be an academic or a professional.
Academics are people who study and teach for a living.
Professionals are people who are an expert at something, and usually get paid for it.
If these people want to talk to people about what they do or explain to others why what the do is important, they need to learn public speaking skills. Which means that they need to learn to not be shy around other people, know how to say things clearly, and in a way that is funny, interesting, and makes sense.
Keep practicing and you'll get there occasionally.