Have you ever met someone who seems to go through life with a permanent spotlight? Someone who's exuberant, lively, and the life of every party? Congratulations! You now have a good impression of Aino Minako, Sailorvenus. Her long, pale blond hair and cobalt-blue eyes emphasize her beauty; she's athletic and playful, and next to Sailormoon, she is the most effective of the inner senshi.
Sailorvenus is a special case. She didn't have to wait until she met Usagi-chan to be awakened. She actually fought alone for a while as the self-proclaimed fighter for justice, Sailor V, accompanied by her white cat Artemis. The video game Sailor V, so often played by the other girls, was originally created by Artemis to train Minako's reflexes. (Takeuchi-san also wrote a few books, called "Codename wa Sailor V," about Mina-chan alone.)
When the inner senshi had awakened, she came out of nowhere, saving Sailormoon from Zoicite, and assuming her persona of Sailorvenus. In the Silver Millenium, she was the leader of the inner senshi, sworn to protect the Moon Princess. She took up this duty again, right away: in order to protect Usagi's identity, she posed as the Moon Princess, hoping to draw the Dark Kingdom's fire. (In reference to this, she was also called the "illusion justice fighter.") This was fairly easy, as Usagi hadn't regained her memories yet. (The deception backfired when Usagi almost got herself killed trying to save Venus.) Because she is the leader of the inner senshi, she feels great responsibility towards them.
Minako, as her "normal" self, is the most playful and fun-loving of the senshi. She's about as bad at school as Usagi-chan, and has a tendency to make puns and mix up her kanji. Her goal in life is to become an idol. It doesn't matter that her other persona, Sailor V, is already a heroine; Mina-chan wants to be liked and admired for herself. She cares deeply what other people think of her and is very self-conscious of her image.
She doesn't like policemen very much, but this stems from her run-ins with the police as Sailor V. They didn't like the fact that she was stealing their glory, and she didn't like how they always got in the way. When two policemen admired Rei, Mina almost blew up at them. Minako has a close friendship with Rei, half-competitive, half-respectful.
Mina's relationship with her cat Artemis is very strong; often it seems that Artemis is in some way directly connected with Sailorvenus' power. Artemis was the one who originally trained Mina to be a senshi. As Sexylyon points out, another indication of the closeness between the two is that where the other senshi got their new powers from their inner guardians, Venus got hers from Artemis. Does this imply that Artemis is the source of Venus' strength?
Sailorvenus holds the star seed of the planet Venus, of course. Her last name "Aino" translates directly to "of love," and "Minako" can become "child." Her attacks are based on love and beauty, i.e. "Love Crescent Shower" and "Rolling Heart Vibration." It's also worth mentioning that the Roman goddess Venus was the deity of love and beauty, and that the kanji for the planet "Venus" is "Metal Star" -- which could explain the "Love and Beauty Chain" that Venus uses in her attacks.
The senshi couldn't do without Venus. She's the leader, and a motivating force. Her normal self may be playful and irresponsible, but as a senshi, Venus is all business, and an extremely effective fighter.
For a closer look at Venus...