A blockquote is a special HTML format that sets selected text apart from the other text in your posts or pages. The style of the blockquote is determined by your theme, and may include a different font style, size, or color, indentation of text, a colored bar at the margin or a colored background. Click the quotation mark on the Visual Editor bar of a post or page to start a blockquote, and click it again at the end of your blockquote material.

Here is what a blockquote looks like in the GeneratePress theme.