Fisrt galaxies and other distant objects are very dim (or invisible) at visible wavelenghts of light, because that ancient light reaches us infrared light. The JWST would detect near infrared (IR) and mid IR light that is 400 times fainter than current space-based telescopes can see.
Primary Mirror. Measuring 6.5 meters across. The mirror is comprised of 18 ultra-lightweight metal beryllium gold-plated hexagonal deployable segments.
The James Webb Space Telescope was launch on christmas day in an Ariane rocket from French Guiana. It successfully completed the deployment of its 70-foot (21-meter) sunshield on Tuesday Jan 5, 2022. The 7-ton JWST is so big that the sunshield and the primary gold-plated mirror had to be folded for launch. The sunshield is especially unwieldly — it spans 70 feet by 46 feet (21 meters by 14 meters) to keep all the infrared, heat-sensing science instruments in constant subzero shadow. Only with this tennis court-sized barrier will Webb have the sensitivity to detect the signals coming from the most distant objects in the Universe, distant galaxies and planets orbiting distant stars.
After launch and after 1 month on a transfer trajectory, the JWST observatory will operate at approximately 1.5 million kilometres from Earth, in an orbit around the second Lagrange point of the Sun-Earth system, L2.