Thus, the Ark in the Tabernacle contained the Torah both engraved in stone and written on parchment. The difference between engraved and written letters is that the engraved letters are part and parcel of the stone, whereas written letters are not part of the parchment but added to it. Thus, engraved letters express our intrinsic connection to the Torah, whereas written letters allude to how we preserve our connection to the Torah even during our mundane lives, when we think of ourselves as being separate from the Torah.
The presence of both the engraved Torah and the inscribed Torah within the Ark indicates that we must first experience our intrinsic connection with the Torah and then carry that experience with us into our mundane lives.1

Thank you so much for this explanation. Now I can understand why our Creator commanded Moshe to place the written part of the Torah alongside the ark! This is so interesting, I spent years wondering why and I learned so many worldly reasonings about it but now I can see that's very important to keep His Law in our hearts at all moments and to put it into practice. In that way, it will be our helper (stand by us) but if we disregard it, it would be as if we are "erasing it or ignoring it" so it is up to us whether we enforce it in our lives or we don't.