Explanation:
In the context of databases, indexes are used to improve the performance of queries by providing a quick way to locate data. Indexes can be ordered or unordered, depending on whether the data is stored in a specific order or not.

Ordered Indices:
- Ordered indices are indexes where the data is stored in a specific order, typically based on a key.
- The key could be a primary key, a unique key, or any other column in the table.
- The data is physically stored in the same order as the key values in the index.
- This allows for efficient searching, as the data can be located quickly using binary search or other algorithms.
- Examples of ordered indices include primary indices, clustered indices, and B-tree indices.

Primary Indices:
- A primary index is an index that is based on the primary key of a table.
- The primary key is a unique identifier for each row in the table.
- The primary index stores the data in the same order as the primary key values.
- This ensures that the data is physically stored in a specific order, allowing for efficient searching and retrieval.
- Primary indices are typically used for tables with a significant amount of data and are frequently accessed.

Clustering Indices:
- A clustering index is a type of index that determines the physical order of the data in a table.
- The clustering index is based on one or more columns in the table.
- The data is physically stored in the same order as the clustering index.
- This allows for efficient retrieval of data that is stored together in the same block or page on disk.
- Clustering indices are useful when there is a high degree of data locality, meaning that related data is frequently accessed together.

Secondary Indices:
- Secondary indices are indexes that are based on columns other than the primary key.
- They provide an alternate way to access the data in a table.
- Unlike primary indices, secondary indices do not determine the physical order of the data.
- Instead, they provide a separate structure that points to the location of the data in the table.
- Secondary indices can be used to speed up queries that involve columns other than the primary key.

Conclusion:
- In summary, indexes that are ordered are referred to as "ordered" indices.
- This includes primary indices, clustering indices, and other types of indices that store the data in a specific order.
- These indices allow for efficient searching and retrieval of data, improving the performance of database queries.