Added question "What is an index in a database?"
diff --git a/README.md b/README.md
index 0ec5262f7..208a44741 100644
--- a/README.md
+++ b/README.md
@@ -8897,6 +8897,13 @@ A single data source (at least usually) which is stored in a raw format.
 <summary>What is OLAP (Online Analytical Processing)?</summary><br><b>
 </b></details>
 
+
+<details>
+<summary>What is an index in a database?</summary><br><b>
+
+A database index is a data structure that improves the speed of operations in a table. Indexes can be created using one or more columns, providing the basis for both rapid random lookups and efficient ordering of access to records.
+</b></details>
+
 ## Regex
 
 Given a text file, perform the following exercises
diff --git a/images/aws.jpg b/images/aws.png
similarity index 100%
rename from images/aws.jpg
rename to images/aws.png
