What does Overhead mean in physical database design?

I just read about physical design and database tuning and I couldn't understand the concept of overhead, and consequently I couldn't understand what the author of the book wanted to explain.

I previously understand overhead as being a overhead or overwritten.

Author of the book.

To the removal and creation of new indexes is a overhead that can be justified in relation to improvements in the performance.

I understand and it made me seem coherent that the creation of indexes in tables, helps in the speed of the queries made in it, but I do not understand how the opposite (the removal of the indexes) helps in performance, as the author states.

Comments

In this answer the author states that it does not matter much the context in which the word is used, in this context does this answer proceed?

If the community understands that my question can be answered by the answer quoted above, then I will remove it.

Book : Database Systems, 2011. Elmasri R, Nevathe B, chap 20, pg 495.