Use of the words

Hi. The entry for the word "pawnbroker" in the Collins COBUILD Advanced Learner's English Dictionary is this:

A pawnbroker is a person who lends people money. People give the pawnbroker something they own, which can be sold if they do not pay back the money before a certain time.

My first question is whether the phrase "the pawnbroker" after the verb "give" in the second sentence is a general, categorical use of the word "pawnbroker" and that's why a definite article is placed before it.

My second question deals with the use of the words "a person" and "someone." Could we replace the phrase "a person" with the word "someone" in the first sentence of the entry after the verb "is"? Thank you in advance for your help.