Every triad contains a root note plus two other notes, the 3rd and the 5th. For minor triads the 3rd is a flat 3 but we still can say out loud ‘3rd’ and it has all the meaning we need in context of discussing minors.
The order always follows in strict rotation. Root is followed by 3rd is followed by 5th is followed by root is followed by 3rd etc. No matter the starting point, the order is the same. When I write ‘order’ I mean the pitch of the notes ascending - think of going around the note circle clockwise.
The shapes I have shown do not really have fixed names that people conventionally use. They do frequently get referred to by their properties derived from the internal order of the intervals. When the root note is the lowest, a triad is in ‘root position’. When the 3rd is lowest, a triad is ‘first inversion’. When the 5th is lowest, a triad is ‘second inversion’.
People also sometimes describe them using the CAGED system and each can be viewed as a fragment of a fuller CAGED shape barre chord. The shape I have labelled Root is a fragment of an A-shape chord. The shape I have labelled 3rd is a fragment of an E-shape chord. The shape I have labelled 5th is a fragment of a C-shape chord. Many people describe that last one as being from a D-shape chord (which is also simultaneously true) but I prefer to view it as coming from a C-shape.
I am trying to negate the need for all of this theoretical understanding, all of this prior learning and knowledge, and simply give them a name we can all use and understand at the outset. I also hope it will be useful in the longer term.
I did not want to name them shapes 1, 2 and 3 because the logic does not follow. Shape 1 could be the shape with the root note lowest. Shape 3 could be the shape with the 3rd lowest. But shape 2?
Additionally, when we eventually move to a different set of three strings (D, G & B strings for example), the shapes change and we need to learn three new shapes for both major and minor respectively. They could not reasonably be called shapes 1, 2 & 3 because they are different shapes. They could be called Root, 3rd and 5th and the logic and sense of following the same naming structure remains intact.
If some or all of that is too much information then please do not get bogged down in it. Simply accept the naming I have used, know that other ways of describing them exist and move on to actually playing them and getting your fingers used to forming the shapes.