Washington doesn't actually use the word "neutrality" in this short statement, so technically it's titled "A Proclamation," but generally everyone refers to it as a neutrality proclamation. That's literally what it is. Washington also mentions it in his farewell address, when he refers to "my proclamation of the twenty-second of April, 1793" (44.1).

Washington issued this proclamation independently of Congress after war broke out between France and Great Britain in 1793. His Cabinet (and the American people) was increasingly divided between favoring France or Great Britain, although they wanted to stay out of the conflict. One of the biggest questions was what the United States' relationship to France was since they'd been allies in the past (source).

Washington soon issued this short executive statement, which argues that it's in the United States' best interest to "pursue a conduct friendly and impartial toward the belligerant Powers" (source).

Not only does Washington declare the United States "impartial" in the conflict between France and Britain, but he says it's illegal for anyone to help or hinder either foreign power or to illegally transport goods for one of them. Anyone who does can be prosecuted.

The neutrality proclamation wasn't loved by everyone, primarily because Washington issued it by executive power and not through working with Congress. It wasn't that Congress or the American people wanted to get pulled into the war, far from it—but they wanted to be involved in the decision. Three years later, though, in his farewell address, Washington is still trying to convince people that neutrality is crucial.