The emphasis is on the differences that people have on the basis of gender, race, sexual orientation, ethnicity, etc. When people come from such different backgrounds, they usually tend to encounter difficulties in managing their relationship with others. This is mainly because people have their ways of thinking, practices, value systems and even prejudices.
However, diversity can be transformed into an asset if individuals develop awareness of their differences and learn to respect them.
Some believe diversity as a step before inclusion, check this article about the difference between diversity and inclusion.