Today most schools are teaching touch typing (using a keyboard) rather than penmanship (writing with a pen), before the use of the keyboard people were required to learn hand writing, Even though calligraphy is an art form you can see many examples of its everyday use in (wedding announcements, births , graduation diplomas etc).
Those not familiar with the difference between lettering and calligraphy think it is the same thing and because of this it can be difficult for them to differenciate between them.
The basic difference between them is that lettering is drawn (made up of different parts), whereas with calligraphy it is written using a single stroke making it an expressive type of writing.
Traditionally calligraphy is done with the use of a quill or dip pen and because of the nibs design the calligrapher or writer can use various amounts of pressure on the nib to produce lines of various thicknesses (widths).
Calligraphy has a rigid set of rules governing the height of the letter, line spacing and angles, which are crutial parts of the system which helps in creating the visual flow of the writing. Whereas with lettering the rules tend to be relaxed (bent) in a tasteful manner to produce fundamental combinations
Lettering on the other hand focuses more on the overall combination as a whole. In lettering composition, the relationships between letters and words are much less rigid and systematic than in calligraphy and regularly include multiple styles. or by the addition of illustrations, ornaments, etc.to add more character to the piece.