Hieroglyphs are images of objects from Egyptian life. These glyphic images can be used to represent sounds or ideas.
A hieroglyph can be used in several ways:
sound - the spoken sound of the object
things - the object itself
ideas - an idea associated with the object
Phonogram (phono = sound + gram = writing) hieroglyphs represent the sound of the object shown.
Phonogram characters are classified by the complexity of their sounds. The simplest sounds are single consonant sounds, this group of hieroglyphs is known as the alphabet. There are 25 hieroglyphs in the Egyptian alphabet. These monoliterals (mono = one + literal = sound) represent the simplest written sounds. They were used when it was necessary to spell things out, like names.
Single literal sounds can be combined to form more complex sounds represented by other characters.
Biliterals (bi = two + literal = sound) are hieroglyphs that represent two consonant sounds. A single biliteral hieroglyph is the phonetic equivalent of two alphabet characters. Three consonant sounds are called triliterals. They are the same as the sound of three alphabet characters.
Often a hieroglyph that might represent the sound of an object when used in one context but might be used to represent the object itself too. In this context it's not a spoken sound, but a literal representation of the object.
In the case where a hieroglyph is meant to represent the object, not the sound, the symbol for one is placed after the object. It's a way of saying 'one of '. This means the character should be read as a literal representation of itself. Used in this context, this hieroglyph is called the ideogram symbol. Adding the ideogram symbol means the object it accompanies should be read literally.
This is an example of how the ideogram symbol is used:
Determinatives are symbols that aren’t spoken. They add meanings to other characters by accompanying a group of phonetic characters to imply a meaning. Typically a determinative character would appear at the end of a word to assist with it’s interpretation.
Here's a modern determinative used with the ant symbol:
In this case, the addition of the silhouette of a woman implies that the sound relates to a woman and makes the meaning 'aunt'.
So a single hieroglyph can act as a sound or thing or idea, depending on context. A hieroglyph's meaning can be affected by accompanying characters and might have different meanings depending on the characters it accompanies.
For instance, the addition of an ideogram symbol might change a phonetic character into a literal reference to the thing shown. Or a character that is phonetic can also be modified by a determinative character that relates an idea or imparts meaning but is not spoken.