Bnha_s3_05_pro_ab.mkv -

A Matroska multimedia container format commonly used for high-definition video files.

The League of Villains' Vanguard Action Squad launches their assault on the training camp. BnHA_S3_05_Pro_AB.mkv

This likely refers to the release group (or encoders) or specific audio/subtitle tracks (such as "Audio Japanese/English" or a dual-audio release). A Matroska multimedia container format commonly used for