That means its trip curve and ratings are tuned for the inrush and overload profile of a transformer primary, not a motor — the Trip Class 10 characteristic gives you a fast enough response to protect the winding without nuisance tripping on magnetizing inrush.
The S00 frame size gives you a 45 mm wide body with 97 mm depth and height — about two standard MCB modules wide, so it fits neatly into a motor control center or distribution board. That zero forward clearance means it can sit flush against a panel door or busbar cover without extra standoffs. Screw-type terminals on the main circuit accept 2x 0.75–2.5 mm² or 2x 4 mm² solid/stranded; M3 screws on the main contacts. Use a Pozidriv size 2 tip with a 5–6 mm diameter shaft. Mounting position is any — handy for tight enclosures where you have to lay it on its side.