The X-Men rose from extremely humble origins to overtake Marvel's most popular characters. X-Men comics are the bestselling comics of the last 40 years, and they've become a fertile corner of the Marvel Universe. New fans are always getting into the X-Men, and that can be rather difficult. X-Men history is quite convoluted and has a reputation for being opaque to new fans. However, there are some pieces of lore that every new fan needs to know.
Source：https://www.cbr.com/xmen-vital-lore-new-fans/
