A stop is a consonant sound produced by obstructing airflow in the vocal tract by the lips or tongue thus increasing pressure, and suddenly releasing the obstruction. The released airflow produces a sudden impulse in pressure producing an audible sound.
English has the following stops:
[p], [t], [k] (voiceless)
[b], [d], [g] (voiced)
[m], [n], [ng] (nasal) ([ng] is here used to represent the velar nasal stop, whose IPA symbol looks like an n whose right edge curves backwards like a j)
[ʔ] (glottal stop)
See phonetics, fricative, affricate, nasal, approximant, click, phonation, airstream mechanism