Basically you have two components:
1> Metrics Designer - It's like a Framework Manager tool. You create the Metric Package, define the Metrics and create the metric extract here. It does not only read the data from the source but also writes the data to another database called Metric Store. This process is called extract (like an ETL).
2> Once you have your metrics defined, then you open the metrics in Metrics Studio and do all the fancy stuff like creating diagrams, reports etc.