Categories of font

As the typefaces are categorised so to are the fonts within each typeface. Some typefaces have more fonts than others. These categories are based on:
Line weight
Light
Roman / Regular
Semi-bold
Bold
Black
Extra black
Character proportion
Ultra condensed
Condensed
Extended
Character angle
Italic
Italic is typically used with serif typefaces. It was created to simulate the slanted style of handwriting. Italic differs from oblique in that the letterforms are often quite different from the roman face.
Oblique
Oblique text is typically found on sans serif typefaces and slants the letters forward. With oblique the letterforms are not changed, just slanted.