Here is 2 FAQ from NASA website:
- What are the main science goals of Webb?Webb has four mission science goals:
- Search for the first galaxies or luminous objects that formed after the Big Bang.
- Determine how galaxies evolved from their formation until the present.
- Observe the formation of stars from the first stages to the formation of planetary systems.
- Measure the physical and chemical properties of planetary systems and investigate the potential for life in those systems.
- How far will Webb look?One of the main goals of Webb is to detect some of the very first star formation in the Universe. This is thought to happen somewhere between redshift 15 and 30 (redshift explained in question 45). At those redshifts, the Universe was only one or two percent of its current age. The Universe is now 13.7 billion years old, and these redshifts correspond to 100 to 250 million years after the Big Bang. The light from the first galaxies has traveled for about 13.5 billion years, over a distance of 13.5 billion light-years.