with Grease Pencil it's possible to have 2D art in the 3D environment, this is especially handy when adding some details to animations without much hassle
it's also possible to make traditional 2D animation with Grease Pencil
to export Grease Pencil strokes to ILD Render enable it in Render Properties - ILD Render Export:
Grease Pencil Render Options
Layers Separate: Uses GP layers as ILD Render layers
Use Fills: take the fill of GP objects into account, only useful for 2D
Grease Pencil options for every GP object
Render Hidden Strokes: normally the plugin checks while exporting if a GP point is visible (hidden behind a 3D object), to disable this check this option
Replace Black with Fill Color: use the fill color if the stroke is black