Glass pliers are used to break glass apart after cutting, some pliers can also shape cut glass pieces. Pliers come in many shapes and sizes: breaking pliers, running pliers, grozing pliers, combination breaking and grozing pliers, from cheap to expensive.
Each of these types of pliers can be used to complete the cutting process. Pliers are are one of the most used glassworking tools, many artists have a large variety of pliers, others have one or two.
An online search will show you the many styles available and their uses.
The general purpose of pliers is to assist in separating fusing glass after scoring by a cutter With long straight scores some people snap the glass by hand, others much prefer to use pliers.
Where the score is short, close to the edge or curved, pliers can be the best option.
The most multi function of the pliers are grozing pliers.