A beggar is a poor person who asks others, or begs, for money or food. Another word for a beggar is a "panhandler," although both terms are vaguely offensive. No one wants to be a beggar.
Many people who are beggars are also homeless and haven't been able to find jobs. Sometimes people use the word in an informal, pitying way: "Poor little beggar, he works so hard!" Another informal term is "to beggar belief," as when something is so incredible that you find it hard to believe. Another expression is “beggars can’t be choosers” which means you get what you get and you don’t get upset.