Difference between index and unique index

I want to know is there any difference between index and unique index. This may be a simple one but i am confused . Please provide me a valid info


unique index – Unique indexes guarantee that no two rows of a table have duplicate values in the key column (or columns). 

when we have define a column as a primary key/unique constraint then an index will be created automatically for that column.

index - create index on the columns using "create index command" to retrieve the rows faster.

I will acts like a book index.

Answer is