Consonants are formed by interrupting, restricting or diverting the airflow from the lungs through the mouth in a variety of ways. We can describe these as:
1. the manner of articulation
2. the place of articulation
3. the force of articulation
The manner of articulation refers to the interaction between the various
articulators (the tongue, lips and teeth, the alveolar ridge, the palate, the velum, and the nasal cavity) and the airstream. The manners of articulation are:

• plosive
• affricate
• fricative
• nasal
• lateral
• approximant

The place of articulation deals with what the articulators do.

Regarding the force of articulation, the following terms are used: fortis or strong, and lenis or weak. In spoken English, ‘fortis’ or unvoiced sounds, which require a more forcefully expelled airstream than ‘lenis’ sounds, which in English happen to be voiced. This distinction is most useful in understanding the difference between sounds that are articulated in essentially the same way, one using the voice, the other not. For example, the sound / p / which is unvoiced and fortis and / b / which is voiced and lenis).
The difference between unvoiced and voiced sounds can be felt by touching your Adam’s apple while speaking. You will feel vibration for the voiced sounds only.

The tables on the following pages are similar to those in the previous
chapter on vowels, except that the pictures show the positions taken by the
various articulators when these sounds are produced. ‘Pairs’ of sounds are
shown together. Unvoiced sounds like /p/ are shown on a grey background.
Voiced sounds like / b / are shown on a white background.

The following diagram illustrates the ‘place’ of articulation.