STAM stands for “Sifrei Torah, Tefillin, and Mezuzot” – in other words a scribe who writes Torah Scrolls, Tefillin (phylacteries), and the Mezuzot that are put on the doorposts.
http://soferstam.co.il
(image from above site – please go there to learn more).
A “Mezuzah” is often considered the box placed on the “doorpost” of a house. In actuality, the “Mezuzah” is the scroll inside the “Mezuzah case”.
Also called a “SOFER”, who goes to school to learn the art and science of writing the letters required for important Jewish documents. Just like a MOHEL (man who does circumcision), or the SHOCHET (the ritual animal/meet slaughterer) has special training, so does the SOFER.
Video: Stam Hebrew Letters
Other related links:
http://www.soferstam.co.uk/soferstam-stam.html