In Data warehousing, levels are columns available in dimension table. Levels are having attributes. Hierarchies are used for navigational purpose; there are two types of Hierarchies. You can define hierarchies in top down or bottom up.

1. Natural Hierarchy: Best example is Time Dimension - Year, Month, Day etc. In natural Hierarchy definite relationship exists between each level

2. Navigational Hierarchy: You can have levels like

Ex - Production cost of Product, Sales Cost of Product.

Ex - Lead Time defined to procure, Actual Procurement time,

In this, two levels need not to have relationship. This Hierarchy is created for navigational purpose.