Why is it important to keep people's "intersections" or
complex identities in mind?

Intersectionality is a framework for conceptualizing a person, group of people, or social problem as affected by a number of discriminations and disadvantages. It takes into account people's overlapping identities and experiences in order to understand the complexity of prejudices they face.

(In the business world, understanding intersectionality is an important part of practicing inclusion because it defines how different facets of identity contribute to our unique perspective and team participation, as well as the ways in which different types of discrimination overlap with one another.)

2018 means 2018 ce or common era

there have been other eras too including bce, which included way more years.