It's called directional drilling [0] and is related to milkshakes [1]

0 - https://en.m.wikipedia.org/wiki/Directional_drilling

1 - https://m.youtube.com/watch?v=a5d9BrLN5K4&pp=ygUddGhlcmUgd2l...

Drilling through more conventional formations (oil or gas) that didn't need fracking. Particularly on formations with large, flat layers it could greatly reduce the number of wells needed, vs. vertical drilling. It's also very useful for offshore drilling.

Measurement-while-drilling (where instruments in the drill string sense the surrounding formation, allowing it to follow ups and downs in the layers) is quite a technical accomplishment. Think about the problem of getting data back to the surface.

Construction projects frequently use it on a small scale when excavation or disturbing existing infrastructure isn’t possible. For example, you need to lay an electric cable for a new development across a road and you can’t shut down the road, so you drill horizontally underneath it and run the cable through.