There are some differences in these terms that should be pointed out separately.
- Modifier (can be also called Modifier tool) is a Challenge tool that can process modification scripts.
- Modification (can be also called modification script, Modifier script, or just script) is a script that contains instructions for the Modifier to modify a map.
- Challenge is a modification or set of modifications applied on a map. Example: A01.Reverse - Reverse here is the challenge, because the modification was applied on the map. A01.Reverse+Checkpointless - Reverse + Checkpointless is the challenge because you applied two modifications on the map.
If you say just Checkpointless, it can mean modification or challenge, but if you say Reverse + Checkpointless, then that can be only a challenge.
!! Therefore remember, challenge script is an incorrect term.