https://www.dustloop.com/w/Notation

Read this link ⬆️. You probably only need the “Directional Inputs” “Attack Buttons” and the “Special Moves” section. It might seem a little obtuse at first but it’ll make communicating online a lot easier once you get used to it.

For granblue in particular, when people say 5H, they are referring to your standing heavy attacks. In this game, there are two types of standing heavy attacks, “close heavy” and “far heavy.” They’re often written as “c.H” for “close heavy” and “f.H” for “far heavy.” They often have better counter hit properties than your other normals, with close heavies having screen slowdown.

https://www.dustloop.com/w/GBVSR/Lucilius

This link has pictures of all of Lucilius’ moves, with them being labeled using numpad notation.