‘Type’ is a word and the ‘T’ is the character/letter.

Meanline is the invisible line where the upper end of lowercase characters touch.

Baseline is the invisible line where all characters sit.

Cap Height is the height of the capital letter measured from the baseline.

The entire space occupied by characters is the font size. Sans Serif and others display typefaces might have large x-heights.

X-height : The distance between the meanline and baseline is known as the x-height.

Leading / Line Spacing is the spacing between two lines ( Alt+up/down arrow ).

Tracking – overall character spacing.

Kerning – optical/custom character spacing ( Alt+left/right key ).