A consonant is sound that is made when the airflow is blocked by either by your lips or your tongue. The different places where this block may occur are called "points of articulation."
It's important to know the difference between these types because the length of a vowel that precedes a consonant is determined by whether the consonant that follows it is voiceless or voiced.
Also, knowing whether a sound is voiceless or voiced will help you to correctly pronounce letters such as -ed and -s ends of words.
Vowels are longer when followed by a voiced consonants. They are shorter when followed by a voiceless consonants. Even short vowels like /i/, /ɛ/, /ɘ/, and /ʊ/ are prolonged when followed by a voiced consonant.
Consonants can either be "stops" or "continuants", depending on the airflow is stopped or if it is continued.
Americans generally do not release many of the final stops.
The final stop is always held when the next word within the same sentence beings with a consonant.