Usually I think people mean being physically able to do something. Like finger technique meaning able to play fast or articulately. Octave technique, playing octaves fast.
More like machinery. If someone says so-and-so has good technique, they mean they have the physical ability to do something well. They're not getting held back by not being able to play fast enough or quiet enough. And they can do those things with ease too. They're comfortable with it. It's not an issue.
It could be an insult too if someone says so-and-so's playing is very technical. Not expressive, but technical. Just a machine.
Training technique? I made up my own daily routine of things to do. That's worked for me, but it's not a piano thing. Pianists seems to get technique by playing pieces. Although... I think that really means 'using' a piece of music as a vehicle to develop physically. Not necessarily performing the piece well in the end. You play an etude, maybe badly, but you get scales or octaves faster. You've developed technique that way. Do that with enough pieces, and after awhile you've developed that technique and can play those pieces at a performance level.
Personally, I see technique as anything involved in getting you to the end goal. Physical technique, mental technique... like reading, understanding, emotional technique... like being able to feel the piece or know what the character of that section is and knowing if that's getting across in the sound.