understand autolayout part 1

To provide Equal width and height from pin menu, you’ll have to cmd+click both parent view and your view then select the pin menu and check equal width/height option.

This constraint is little tricky and generally used with labels only. Baseline and bottom appears same but are not, since when you align using baseline


understand part 2

First Item — View from which you applied the constraint.
Relation — Relationship or the comparison operator that will be applied between the values to which this constraint is applied.
Second Item — View to which you applied the constraint.
Placeholder constraint is just a feel-good constraint that will be removed at build time and Xcode will force put the constraints to satisfy if that breaks the layout. Installed will tell whether the constraint is active or not and this generally makes sense when we are working with size classes.

First Item.attribute = (Second Item.attribute * Multiplier) + Constant