Props, short for "properties" are a part of even the simplest stage production. Though shows of course exist that require no props at all, being in theatre you are likley to have at least one or two you need to become familiar with, depending on the show.
Note that I said, "become familiar with" and not simply "use". For when I use a prop, I like to become intimatley aware of as many facets of it as possible. This is especially true for hand props. (Those carried by an actor.)
Some reasons for this are obvious. Practicality, and ease of use. How heavy is the object? Can it be thrown easily if needed? Can I carry it in a pocket? Though one could proceed to use a hand prop without taking these things into consideration, mostactors do take inventory of such things, so as not to appear akward and clumsy while on stage using the prop. Common sense which I would guess 90% of actors agree with.
Yet there are other reasons to become more intimatley familiar with the particulars of a prop. Reasons that are more nuanced, and details that would seem unimportant to many.
An object used by a character, especially one that is written to be used frequently, should be an extension of the character, and hence the actor portraying the character. If we mimick real life onstage, we must acknowledge that the objectwe use everyday are usually familar to us in more than a passing, utilitarian sense. We know the practicals, but also the incidentals to that specific prop. Details that may not, in an of themselves improve a performance, but when taken together lead to a more intimate familiarity with the object. It is said familiarity that ehnaces a performances, even in the most subtle of ways.
I would estimate that 75% of actors I have worked with, for this very reason, will carry their hand prop around with them back stage, or in the green room before their scene. I know I do. Themore I carry it, the more details about it I assimilate into my consciousness of the object.
If you want to have some fun one day, talk to actor friends you know during a run of a production. Ask them about any hand props they use. At first they may simply mention what it is. (ex. A briefcase). But if you are so inclined to press further, I am willing to state that most actors will be able to tell you other things about said briefcase that you would never imagine would matter. There is a small piece of fake leather lining that curls up on the bottom right hand corner. A cigarette burn the exact size of one's pinky near the handle. A "John Doe was here" sort of scribbing in an obscure inside compartment. The little things.
Again, none of the above details would matter greatly to most people outside the theatre world. Nor would they matter to a portion of people in theatre. But for me, and many I know, that scribble, that burn, and piece of pleather gives character to the prop. It gives it a lived in feel. And though the details may not be seen by the audience, such character traits can combine with the character traits the actor is trying to convey. They contribute to the ultimate goal of just about any production...similarity to life.