By and large, so-called PUAs are inexperienced people talking scarily ignorant shit at each other to try and appear more experienced than they are, or have some degree of success - if it can be called that - which amounts to having sex with a string of women as ill, sociopathic and/or desperate as they are, or ones who are too stupid to realise what a scary manipulative misogynist the person edging ever-closer to them is.
In other words: they have the amount of sex they would otherwise have if they were just perfectly honest about their ends, minus all the people they've scared off by being clearly desperate and/or not very well in the head.
2. One who can and does successfully meet women and collect phone numbers, go on dates, and eventually has intercourse with his desired females.
3. One who uses psychology and/or sociology in order to get what he wants from the opposite or same sex (depending on his or her sexual preference), and has a large success rate.
4. One who studies and practices the art of Pickup, which includes several different areas of study (including social dynamics, psychology, sociology, body language, etc).
5. Term made extremely popular by Mystery and his show on VH1, which taught "losers" how to talk to women and build their self confidence, and transforming them into "pickup artists". Also made popular beacuse of the book "The Game" written by Neil Strauss which explains his transformation from a "nerdy" writer for Rolling Stone Magazine into an internationally known pickup artist.
Normal men do not have such a strong skill set due to shyness, hence they have a very slim chance of success with hot women who see right through their bullshit and proceed to either shoot them down or use them.
A Pickup Artist is a man that DOES have this social skill set due to the sheer amount of time he has spent interacting with women, but has done so through determination and hard work.
Pickup artists, like the rest of us, enter relationships to have sex. However, pickup artists realize that they are in high demand AND have the skills necessary to start a new relationship before one gets too serious
A Douchebag is an attention-whore who uses similar methods for personal gain only, with no regard for how the woman feels.
For this reason, REAL pickup artists follow a "leave them better than you found them" rule.