Answering intriguing and complex questions to people curious and interested in learning physics: the site “Ask CREF”

The article celebrates the ten years of the question-and-answer website developed at the Reference Center for Teaching Physics (CREF) of the Federal University of Rio Grande do Sul. These are questions and doubts, most intriguing and some of a complex nature, whose answers are hardly found in the physics literature. The description, evolution, scope and impact of the site with the Portuguese-speaking community of teachers and students are discussed. Also presented are the ten most accessed questions on the site and, as examples, six complete posts.