I would say that skew is your best option because it can be used to create a slant.
The video on this site articulates the differences between the transform options quite simply, it might be worth a look for you.
"Transform submenu commands
Enlarges or reduces an item relative to its reference point, the fixed point around which transformations are performed. You can scale horizontally, vertically, or both horizontally and vertically.
Turns an item around a reference point. By default, this point is at the center of the object; however, you can move it to another location.
Slants an item vertically and horizontally.
Stretches an item in all directions.
Applies one‑point perspective to an item.
Manipulates the shape of an item.
Rotate 180, Rotate 90 CW, Rotate 90 CCW
Rotates the item by the specified number of degrees, either clockwise or counterclockwise.
Flips the item vertically or horizontally."
Good luck :)