It's called "busking" and it's when a musician or other performer sings, plays their instrument or entertains in some other way on the street for voluntary monetary contributions from those passing by. Some people think that buskers are homeless folks who perform to eat. Of course, isn't that pretty much what everyone does? We perform in some kind of job or business to receive payment so we can eat.
Busking is not at all defined by one's status as homeless or not. There are thousands of people who perform on the street for the sheer joy of sharing their gift of music, magic, miming, juggling, acrobatics, dancing, etc. True, some of those who may busk may actually be homeless, however, I dare say that most of them are not homeless. Further, some of these musicians are very accomplished, many perform professionally in other venues and, on occasion, some are even world-renowned musicians. One recent busking event took place in a Metro Subway station in Washington, DC where virtuoso violinist, Joshua Bell, performed for passersby. It was actually an experiment set up by the Washington Post newspaper to see people's reaction. Bell, of course, was not dressed like he would be for a concert performance, but his playing stopped and moved many people. Two days later he performed in Boston to a sold out audience at $100 per ticket.
I took this photo of one of only a few piano buskers in the U.S. This was across the street from the Pike Place Public Market in Seattle, Washington. I said there are only a few piano buskers because moving a piano around is a weighty proposition. It's certainly more difficult that schlepping a saxophone, guitar, violin or a small case full of magic tricks. For some reason, some cities and towns frown upon buskers and will often either chase them off or require them to purchase a very costly license to perform in public. However, in general, I believe buskers are allowed to perform freely and become part of the local ambience, attracting shoppers and tourists, thus, helping the local economy.
I recall, some 20 or more years ago, chatting with a family of street entertainers on Pier 39 in San Francisco. There was the mother and father and either two or three children, as I recall. There was a permanent stage in the center of the pier with a small, but adequate seating area in front of the stage. I learned in talking with the husband that many of the street musicians on Pier 39, at The Cannery and at Ghirardelli Square made full-time livings at busking. They simply found a prominent location with lots of foot traffic, set up to perform, placed their guitar or other instrument case, or in some cases a hat, in front of them (they often dropped a few dollars and some change in the hat themselves to get the idea across for people to contribute) and then performed. The family I was talking with actually had the kids come down off the stage and pass a hat through the spectators, just like taking an offering at church. He told me they made about $70,000 a year, which was nothing to sneeze at around, 1990 or so.