For those who are not too familiar with these terms, eggshell and satin are two terms that are commonly used in order to describe the type of paint that will be used. The satin paint will make your walls appear almost velvety. There are some that can look glossy depending on what you want.
The eggshell finish is said to have a very subtle sheen which is probably the reason why it has gotten its name. This is the type of paint that people want to use when they want to put some emphasis on their lights. This type of finish can improve the walls without making the walls shiny that the lights will look washed out.