Does this algorithm have a name? (Distance between letters)
This answer is expanding on @mentallurg's comment.
One of the important properties of a cipher is that you can decrypt. More precisely that there is an algorithm that takes in the cipher text and the private key and produces the correct plaintext. (Your scheme does not have a key, which is a separate problem with calling it a cipher).
So let's take your ciphertext &quot;CgZcG HcFHs&quot; and try decrypting it.
C = 3
g = -7
Z = 0
c = -3
G = 7
 
H = 8
c = -3
F = 6
H = 8
s = -19

So I know the distance between the fist and second letter is 3, but I don't know what the first letter actually is. If I knew the first letter then the rest would be uniquely determined. If your alphabet is [a-zA-Z] then there are 52 different plaintexts that would have produced this ciphertext, and the decryption algorithm has no way to know which of the 52 was the intended plaintext.