What is meant by apache spark?

It is an open-source framework and it's scope can't be written in a small discussion. It has been used internally by many cloud service providers. e.g. Azure HDInsight. Below are main use cases, but not limited

1. Process Streaming Data
2. Machine Learning capability
3. Analytics 
4. Fog Computing(IOT)
   

Please read more details here https://www.qubole.com/blog/apache-spark-use-cases/