The Torah scrolls are the tangible manifestation of our connection to God, our greatest treasure and guide for life. "And now," says Moses, "write this song for yourselves" (Deuteronomy 31:19). From this we learn that every Jew must write a Torah scroll.
But this is a very laborious process. Each one has 304,805 letters that must be handwritten, with ink and quill on leather, in a special calligraphy, usually done by a trained scribe.
If you are not one of those scribes, you can have a scroll written for you. But if you cannot afford it, there is another way to fulfill this mitzvah: to buy a letter in a Torah scroll, meaning that the letter has been written for you.
Each individual is like a letter. Which is the most important? The first? The last? One of the Ten Commandments? In reality, if any letter is missing, the entire scroll is invalid. The Jewish people are like a Torah scroll; each individual is important in themselves and contributes to the wholeness of the people.
The Lubavitcher Rebbe, Rabbi Menachem Mendel Scheerson, of blessed memory, began a project called the Children's Torah. Every boy and girl under the age of bar and bat mitzvah can purchase a letter in this scroll. The fifth scroll is currently being written in Old Jerusalem, where all the scrolls are kept. The cost of a letter is $1, and enrolled children receive a special certificate. See http://www.kidstorah.org.