The best way I can describe it is like this:
TSV = Trainer Shiny Value
Every save file in the new gens has a special 4 digit number assigned to the trainer and every egg also has a 4 digit number called an Esv (Egg Shiny Value) if an Egg matches your Tsv it'll hatch as a shiny.
I'm sure there are other places/people who explain it way better though but trust me they're super helpful.
You're welcome.
TSV = Trainer Shiny Value
Every save file in the new gens has a special 4 digit number assigned to the trainer and every egg also has a 4 digit number called an Esv (Egg Shiny Value) if an Egg matches your Tsv it'll hatch as a shiny.
I'm sure there are other places/people who explain it way better though but trust me they're super helpful.
You're welcome.