Serif fonts: such as Times and Courier. Serif fonts have an extra detail at the end of each stroke making them more look more traditional old fashioned and more formal than sans serif fonts.
Sans Serif fonts; such as Helvetica or Ariel. Sans serifs fonts are less formal and seem more friendly and soft with smoother edges for example the Comic Sans font. Some also seem more modern.
The font used 'Palatino' from the serif category on the promotional poster of 'Pearl Harbour' is more traditional and formal.The font conveys the time in which the movie is set in and aspects of historic features.
THE TWILIGHT SAGA- Twilight and Eclipse
The font used for the twilight promotional posters is called 'Zephyr'. This font belongs to the Serif category, the letters have extra little details at the end of each strokes of the letters. Making them slightly more formal and traditional, but also the extra details on the titles like the think overlapping lines on the 'Eclipse' title or the little ornaments on letter 'g' in the Twilight title.