sample readme updated

Author: jerrinot

kafka-questdb-connector-samples/stocks/readme.md

@@ -2,6 +2,10 @@
 ## What does this sample do?
 This sample project demonstrates how to feed changes from a Postgres table to QuestDB. It uses the [Debezium Postgres connector](https://debezium.io/documentation/reference/1.9/connectors/postgresql.html) to capture changes from a [Postgres database](https://www.postgresql.org/) and feed them to a [Kafka](https://kafka.apache.org/) topic. The [Kafka QuestDB connector](https://github.com/questdb/kafka-questdb-connector) then reads from the Kafka topic and writes the changes to a [QuestDB](questdb.io/) table. QuestDB is used for analytical queries on data and to feed the data to a Grafana dashboard for visualization.
 
+The project can be seen as a reference architecture for a data pipeline that feeds changes from a Postgres database to QuestDB. Postgres is an excellent [transaction/OLTP](https://en.wikipedia.org/wiki/Online_transaction_processing) database. It excells with simple short-running queries. Hence, the `stock` table contains only the most recent snapshot of the data. It stores no history at all. 
+
+QuestDB is a time-series database which shines with time-series analytics. It is a great fit for storing historical data. The `stock` table inside QuestDB contains the full history of the `stock` table in Postgres. Whenever a stock price in Postgres is updated the change is written to QuestDB as a new row. 
+
 ## Prerequisites
 - Git
 - Working Docker environment, including docker-compose