What is the purpose of this poster? to urge people to spend money in a certain way to urge people to support a specific person to urge people to believe in something specific to urge people to do something for the good of others

If it's an ad then it's to urge people to spend money in a certain way

If it's say a band poster it's most likely to urge people to support whoever's on that poster

If it's a poster for like vegetarianism or a religious practice then it's to get someone to believe in something specific

If it's a poster for something like Childrens Hospital then it's to urge people to do something for the good of others like donating to a cancer research project or something of the sort.