Outline
While Development Projects are how you advance technologically, Theory Research is how you advance scientifically.
Development Projects are unlocked by Theory Research.
Theory Research is broken down into several fields.
Fields:
Every nation has its own rating for each individual field of Theory Research. This rating determines not only what classes of development project are available, but also availability of government policies and production of different types and qualities of commodities.
A field rating can be increased by investing in Theory Research of that field through the use of Research Labs. Research Labs can work on one or multiple fields at the same time, determined by the player.
A field rating never goes down (once the science is known, it's known), but individual Labs can fall into inefficiency.