Open Stance vs Closed Stance!

Closed Stance

A player's ability to develop both an open and closed stance begins with footwork. The traditional closed stance forehand is struck after a player's non-dominant, or lead, foot has stepped toward the net. If the player were standing on a clock face, the back foot would be at 6 o'clock, and the front foot would positioned at nearly 12 o'clock. The player's feet are almost perpendicular to the net. For a closed-stance backhand, the feet are reversed.

Open Stance

The open-stance forehand is struck after the player steps to the side to line up the incoming ball with the dominant leg. to use the clock analogy again, for a right-hander, the dominant foot is standing on 3 o'clock, and the non-dominant foot is around 9 o'clock (reverse positions for a lefty). In this stance, the player's feet are nearly parallel to the net. For an open-stance backhand, a player will line up the incoming ball with the non-dominant leg.

Work Cited: https://www.active.com/tennis/articles/when-to-use-an-open-stance-groundstroke