A userform may contain horizontal and vertical grid lines to help you align the controls
When you add or move a control it "snaps" to the grid to help you line up the controls.
This option can be switched off (Tools > Options)(General tan, "Form Grid").
The Format menu provides several commands to help you align and position the controls precisely.
Also helps you to space the controls evenly.
When you select multiple controls the last control appears with white handles rather than black.
The control with the white handles is used as the model against which the controls with black handles are compared to.