Add caching content (#1544)

* Update readme.md

* Update content/roadmaps/101-backend/content/110-caching/readme.md

Co-authored-by: Kamran Ahmed <kamranahmed.se@gmail.com>

content/roadmaps/101-backend/content/110-caching/readme.md

@@ -1 +1,3 @@
-# Caching
+# Caching
+
+Caching is a technique of storing frequently used data or information in a local memory, for a certain time period. So, next time, when the client requests the same information, instead of retrieving the information from the database, it will give the information from the local memory. The main advantage of caching is that it improves the performance by reducing the processing burden.