What information does Fuseki DB folder contain

Curious to know what kind of data fuseki DB folder contains (apache-jena-fuseki-2.4.0/DB/). Iam using apache jena fuski 2.4.0 version. Even if I try upload and drop of graphs to fuseki datasets or dataset deletion or normal graph updates, no files in DB get changed and its size remain constant sometimes. Could anyone please help me understand about the data gets stored in the DB folder?