What variables and constants are, and what they are for.
Why type is important, and how to use different types.
What objects are, and how to use classes to make them easy to build reliably.
Why arrays are useful, and the basics of how to manipulate them.
This is already a huge first step! Don't hesitate to go back and practice any exercises where you might be a bit uncomfortable, and when you're ready, try out the Part 1 quiz!