What is the Difference between Cost Center and Dimension
An accounting dimension is just a way of splitting up accounting entries. The accounting dimensions doctype allows you to add other dimensions according to your organizations needs.
You can think of a cost center as a dimension that is built in by default.
Cost Center and Project are standard features at ERPNext which can used to separate Financial Statements
But sometime, you need to know separate Financial Statements for other dimension such as Department, Branch and so on, you can use Accounting Dimension for your specific requirements