When you speak, you avail yourself of words the way a musician uses notes. And like the musician, you can sound words and letters smoothly or disconcertingly. All it takes to be smooth is some awareness of language. The way we speak breaks down into three elements:
Articulation means using your articulators—lips, tongue, teeth, lower jaw, upper gums, hard and soft palate, and throat—to form the sounds of speech. The key to good articulation is keeping all these parts flexible as you speak.
Diction is the total production of your sounds. You can be sloppy or crisp, depending on how you put everything together.
Pronunciation is the manner in which you deliver words; it's where you place your accent. People in different regions pronounce differently—car in New York becomes cah in Boston. I once heard a Russian woman deliver an address on the subject of nuclear power at a public utility. When she said mass (frequently), it sounded to those in the audience like mess and they were noticeably alarmed and confused.
The clearer your articulation, diction, and pronunciation are, the more in control—and the more powerful—you will appear to be.