Este vestido es bonito. This means: This dress is pretty. In Spanish demonstrative pronouns have gender and can be singular or plural. In this case, the pronoun is modifying "vestido" which is a masculine singular noun. So the pronoun must be male and singular as well. The only possible option is "este". The others: "esta", "esas" and "ésta" are all female so they don't apply.
*English* From the reading of the first chapter of the book "Think and Get Rich" Apply the roof of prediction to get a better understanding of the reading.
