yeah, its a surface piercing, barbell stud, thats bent like a staple. You can get them alot of places, front and back of neck, top of wrist, the one in middle of chest looks hot on women when they show cleavage, ive seen them in alot of areas. i used too have 6 of them on mu shoulder blade, but took them out because they were getting irritated from benching/lift where i had to lay down. I dont have any current pictures, just google "surface piercings"
Yes they are the next "big thing"... they've always been around just need to be utilized more.
Yes the muscles are trained differently. Both are amazing. A lot of complaints regarding those movements are regarding flexibility.
For instance in the front squat I find that most people are flexible enough to perform the movement easily. If you can touch your ear... you can rack the bar... just move your elbows in & bam you have the position. Most people that complain about their wrists hurting usually have weak abs and bend forward when they squat downward thus causing the bar to roll into their hands rather than be supported by their shoulders/upper chest/ clavicle.
OH Squats is...everything. Everything has to work. A LOT of flaws can be overcome through overhead squatting.
But you can't really add weight to these unless you have a solid back squat.