The Atbash cipher is a very common, simple cipher. It was for the Hebrew alphabet, but modified here to work with the English alphabet. Basically, when encoded, an “A” becomes a “Z”, “B” turns into “Y”, etc.
The Atbash cipher can be implemented as an Affine cipher by setting both “a” and “b” to 25.
This is your encoded/decoded text:
This is your decoded text: