Scripting is basically when software takes over the control over some actions like combos (Brand Combo etc.). Some scripts can even dodge nearly every skillshot or level up your smurf to level 30 on its own.
There are actually two types of scripts.
- Champion Scripts
Scripts that will pull off hard mechanical plays for you. They only work for certain champions. E.g. ryze skill rotation, when his passive is up (root every 2 seconds) etc.
- Utility Scripts
Utility scripts are scripts that affect your gameplay in general and not for a specific champion.
There are Utility Scripts, which will not be considered as cheating by riot.
For example a script which extends your HUD with a spotify interface so you can change the playing song ingame.
On the otherside there are scripts like automatic jungle timing, ultimate timing, orbwalking assistance, dodging assistance, "last seen"- position of the enemy champions visible on the map and even scripts that will level up your smurf to level 30 in Co-Op vs AI games.
I'm not sure what riot does against scripters I guess they don't get banned really often but I'm not sure.