The MLB Stats Explorer was created using the same data that a lot of the major sports sites use. The data is an aggregation from Retrosheet and Baseball Reference. The data being used in this application was obtained from the Chadwick Bureau's GitHub Repository, the Baseball Data Bank
The data provided by Chadwick is in the format of csvs (which are quite large in size). For this site, I have modeled those csv files in a MongoDB database which is accessible through a REST API that I developed in Node.js. through my REST API written in Node.js
With data covering the majority of baseballs history, there are a lot of statistics we can look into. Players, Managers, Teams, Ballparks, Post Season, Hitting, Pitching, Fielding, you name it, it's available. The goal of the MLB Stats Explorer is to enable user to dig into that data and find what they are looking for. With all of the data available to you, you can easily get what you're after.