OK. So we're talking about a vertical lift, similar to lifting in a lineout.
No. It is a front on, 45 degree, “plane taking off” action in the tackle contest, by one or two players, intent on lifting the opponent off the ground.
Is it a one or two person lift?
Both.
What immediately happens after the lift ... gently lower, drop on feet, drop on head, carry towards goal line, etc?
Aggressive drive toward the opponents tryline, and/or attempt to hold up the player for a maul.
On one occasion two defending players were holding a player in a helpless and prone position fully off the ground. I managed this by insisting that they lower the player to ground gently, which they did. No penalty.
On two occasions the player was near horizontal, and dropped heavily on his hip. Sanction was penalty. Second time a warning was issued to cease lifting. The team complied, despite protests from the coach.
What does the coach hope to gain by coaching this technique?
My guess is to disrupt the playing of the ball, and gain a turnover in the ensuing maul or ruck. In my opinion this technique is good and effective rugby, when done safely and legally while not lifting the player off the ground.