What does disparity mean?

mean similar

Actually, it means the exact opposite of similar. It means "completely different."

To me, it has a slightly different connotation because of how it is used in Information Technology (my field or work/study). In IT, it refers to systems that are completely distinct and cause inefficiencies. For example, you may have two databases that contain the same information. A common example is a company that has separate software for the Shipping and Receiving department and for the Accounting department. In order to get information from S&R to Accounting, someone has to print off a report and manually enter the data into the other system. This would be a disparate system. ERP software would be a solution to this, all departments use the same software with a centralized database and can access the same information.