Ascender, h (the top bit)

Descender, p (the down bit)

Baseline, invisible line underneath text

Cap line/height, height of a capital letter

Uppercase/lowercase (duh)

Kerning, space between two letters that is different to the majority

Tracking, space between each character in a uniform way

Leading, space between baselines (tight or loose)

x-height, the height of a normal letter with no ascender or descender

Stroke, stroke width, the weight of a line

Ligatures, letters that are connected