The part of the play that describes what is happening on the stage is

The part of the play that describes what is happening on the stage is called

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- Exposition.

Explanation:

Exposition is characterized as the 'element or device' of the play that primarily functions to describe the background or context of the play along with the description of the setting and introduction of the characters of the play. It primarily intends to prepare the audience for the upcoming content by making them familiar with the context in which the play took place and its characters, setting, and other vital elements of the plot which would assist them to have a better and comprehensive understanding of the play. Thus, 'exposition' is the answer.

there are number of topics. you can pick any one of these topics:

the illustration   that would give a reader a clear understanding of the text is a picture of men constructing the frame of a building.the frame is made of iron bars. the text describes the job of blacksmiths'. these were very organised and they had different names: "the driver" and "the heater". the text describes the way in which these men worked ; they worked iron pieces as if they were playing a sport. in fact, the text wants to show the men's skills. the text also puts some emphasis on the use of '' rivets'' in construction. this kind of nails were not always used in the construction of manhattan.

some examples:

"and with an underhand toss he hurled the smoking rivet straight at the catcher, who caught it in mid-air in his catching can." men's skills

"when the driver was ready for a new " the emphasis on the rivet ( special nail used in construction).

" it against a beam to remove any cinders, and jammed it into the waiting hole. " the emphasis on the rivet.