E. coli is a bacteria commonly found in the intestines and survives in both aerobic (with air) and anaerobic (without air) conditions. lb broth is a rich medium that is mostly used in the lab for the growth of bacteria while lb agar is a nutritious rich medium used in molecular biological procedures for the rapid growth of bacteria. These mediums provides with a suitable environment for bacteria growth and multiplication since they are rich with all the nutrients and air required by the bacteria. LB means Luria-Bertani the person who came up with the medium.