In the hebrew text of the Torah scroll, thousands of years of tradition dictate how each letter is to be written. Certain words, such as the first word of this week's Parshah, are exceptional in some way.
The opening phrase is "And G-d called to Moses." This is the beginning of the third Book of the Torah, Vayikra (Leviticus). Unlike the preceding book which is mainly narrative, telling the story of the Exodus, this book mainly comprises direct instruction from G-d. So it begins "And G-d called to Moses." G-d called to Moses from the Sanctuary, to teach him the laws which he would transmit to the Jewish people.
The first word in this phrase ends with a letter Aleph. What is unusual is the fact that this Aleph is very small compared with the size of the other letters. The scribe has to write very carefully a tiny Aleph. This has been a feature of every Torah scroll since the first one, written by Moses. What does the small Aleph signify?