Understand typography for sketchbook

• Body Copy: Large blocks of type set to be read with the greatest of possible ease. Body copy should all be set in the same font, with shared point sizes for the face and leading.
• Majuscule: Otherwise known as Uppercase letters. Most of our alphabet borrows its Majuscules from the Latin, or Classical letterforms.
• Minuscule: Counterpart to Majuscule, Minuscules are our lower-case, copied and modified throughout the years to better fit their Classical letterform counterparts.
• X-Height: In a miniscule set of a font, the so called “height” is the space between the baseline and the mid-point, which is often the height of the lowercase letter x.
• Baseline: The invisible line where the fonts “rest.” Descenders can dip below this line, but have a resting point that sits on it.
• Ascender: In the set of Minuscules, the Ascender is the part of the font that goes beyond the X-height, approaching the Capital letter height. Letters with ascenders are those like l, b, f, or k.
• Descender: Also in the Minscules, the Descender is the part that dips below the Baseline. Letters that have descenders are p, q, y and, in some faces, f.
• Ligatures: Sometimes lowercase letters collide within words and create tangent points and bizarre shapes that can cause a reader to stumble without realizing why. Typographers artfully combine letters like “fi”, “ti”, “ffi” in ways that are easy on the eye and are often undetectable as separate characters. Many quality fonts include these Ligatures among their Glyphs.
• Bowl: Enclosed round space within letters like the “o” and “p” or “B”.
• Counter or Counterform: Open rounded space within letters like the “c”, “G” or “U.” The lowercase “e” has a bowl and a counterform.
• Letterspace: The most literal typographic term, Letterspacing is adding blank space between individual letters. It is only adding space and is not to be confused with Kerning. Some fonts are easer to read Letterspaced, while some are harder.
• Kerning: Letters are Kerned when the spaces between letters are closed up, bringing them closer together. Some letter combinations like “AV” often need Kerning to not look awkward and filled with excess space. Most kerning in modern computerized type is done automatically by the software, but may need personalized attention depending on the font or the situation.
• Lead or Leading: Lead is the space between baselines of text in body copy. For instance, “double-spacing” your research paper in Word is increasing the Leading. Leading is set in points and is normally set at the same point as the font or slightly higher. This is pronounced “Lead” as in the heavy metal substance in the case of “Lead” and “Leading.”
• Serif: Serifs are traditional flourishes, points, and shapes on the ends of the strokes of letters. These are hallmarks of older style fonts with roots in Roman, Italian, and German scripts. These were originally part of naturalistic pen strokes and became part of the first sets of fonts. It took longer than you might think for the first fonts without Serifs to be created and and widely used.
• Type Nerd: Exactly what it sounds like, Type Nerds relish pointing out when somebody uses Faux Bold or a Double Prime instead of true quotes. Typography is an art form created by sticklers, and so creates a lot of Type Nerds.

Source: http://www.howtogeek.com/howto/30065/how-to-understand-typography-like-a-professional-designer/