Stud Bolt
Stud has a thread on full lengths or at both ends. As shown in images. It is having three components if washers are not used (two nuts and stud). If you used washer it would become five. Sometimes additional nuts are used for hydraulic tension with larger size stud.

Stud Bolt Specification & Standard
Various ASME standards are used for stud bolts and nuts to manufacturing bolting material. List of such standard is given below.
Diameter and Lengths of the stud and bolt are covered in ASME B16.5 & B16.47
ASME B1.1 Unified Inch Screw Threads (Cores and Fine thread series- normally Cores thread series is used for stud used in piping)
ASME B18.2.1 for Square and Hex Bolts and Screws
ASME B18.2.2 Square and Hex Nuts
ASME B18.21.1 Lock Washers
ASME B18.22.1 Plain Washers
Machine Bolt
Bolts have a thread at one end and hexagonal head on another end. See the image below. In the process, piping bolts are used with lower strength flange types such as GRE/GRP, bronze. Usually, washers are used with bolt to prevent excessive load to the flange.