Dave Strider is one of the principle characters of Homestuck, being introduced in Act I. He is first introduced using an Instant Messenger type program with story protagonist John Egbert, and is then shortly later introduced more directly. Whereas John, the lead, is a straightforward and somewhat naive young man, Dave is presented, in contrast, to be cynical and prone to cursing and insults. He is also the master of irony, which he describes in one of his opening monologues to be a matter of layers and tiers of irony: he is ironic about his own sense of irony, at several degrees removed. One of the products of this irony is the webcomic Sweet Bro and Hella Jeff, a series of fractured, badly drawn stories about two bros. At the start of the story, Dave Strider lives in a skyscraper in Houston, Texas with his older custodial brother, who has similar interests to Dave, and who makes money off of a series of webpages where he ironically targets peoples needs, including by making puppet themed pornography. Both Dave Strider and his older brother are rappers who enjoy (ironically) replica video game swords.
The initial portrayal of Dave Strider is part of Homestuck's comedy of manners about youth archetypes and online personalities, and it is a pretty accurate description: I think we all went to junior high with a cool kid like Dave Strider. However, as Homestuck enters the territory of being an avant-garde and surrealistic science fiction story, Dave Strider takes on a mythological significance, as he becomes a time traveler charged with defending timelines. As his last name and use of a broken sword show, he is also compared to Aragorn from The Lord of the Rings. Rather than just being an odd pastiche, these ideas are fit (more or less) seamlessly together: the story of a teenager using irony to conceal their personality flows naturally into a story about the nature of time and destruction. And, of course, we learn that even with all the layers of irony that Dave Strider used to conceal things, there were many things concealed even from him.
All of which sounds very serious. But much of Homestuck is dialogue driven, and the series creator, Andrew Hussie, has said that Dave's meandering yet sharp dialogue is the most natural to his voice. Homestuck is expansive, and at many points, Dave Strider gets a chance to soliloquize for paragraphs on any given topic, either earth's pop culture, or the increasingly bizarre cosmic situations they find themselves in. Most of those quotes need some context to make sense, but they are some of the most hilarious moments in Homestuck.