Scripts are what sets a botting client apart from the official OSRS client. They control the behavior of the player and dictate what it should do, e.g. fishing, killing zulrah, doing tutorial island, etc.
The SDN (Script Delivery Network) is an online repository of scripts maintained by OSBot for its users. The network is managed by Token, who monitors and checks every script to ensure safety and quality for its users. The SDN contains 3 types of scripts: free, VIP+ and premium. In addition to this, you may also encounter private scripts but those are not on the SDN, and not regulated by OSBot staff.
That depends on your goals, commitment and budget, but for 99% cases, the best option is premium scripts. They have a very good price to quality ratio and suit most needs, whether you are a casual botter training a few accounts, or a hardcore goldfarmer aiming for $10k+/month.
1. SDN script
2. Private (local) script