Answer by taking a quote from the following article:

Hartman was born Philip Edward Hartmann (later dropping one "n") on September 24, 1948, in Brantford, Ontario, Canada. He was the fourth of eight children of Doris Marguerite (Wardell) and Rupert Loebig Hartmann, a salesman specializing in building materials. His parents were Catholic and raised their children in that faith. As a child Hartman found affection hard to earn and stated: "I suppose I didn't get what I wanted out of my family life, so I started seeking love and attention elsewhere."

In contrast to his real-life personality, which was described as "a regular guy and, by all accounts, one of show business' most low-key, decent people", Hartman often played seedy, vain or unpleasant characters as well as comedic villains. He noted that his standard character was a "jerky guy", and described his usual roles as "the weasel parade", citing Lionel Hutz, Bill McNeal, Troy McClure and Ted Maltin from Jingle All the Way as examples. Hartman enjoyed playing such roles because he "just want[ed] to be funny, and villains tend to be funny because their foibles are all there to see."  He often played supporting roles, rather than the lead part. He said "throughout my career, I've never been a huge star, but I've made steady progress and that's the way I like it," and "It's fun coming in as the second or third lead. If the movie or TV show bombs, you aren't to blame." Hartman was considered a "utility player" on SNL with a "kind of Everyman quality" which enabled him to appear in the majority of sketches, often in very distinct roles. Jan Hooks stated of his work on SNL: "Phil never had an ounce of competition. He was a team player. It was a privilege for him, I believe, to play support and do it very well. He was never insulted, no matter how small the role may have been." He was disciplined in his performances, studying the scripts beforehand. Hooks added: "Phil knew how to listen. And he knew how to look you in the eye, and he knew the power of being able to lay back and let somebody else be funny, and then do the reactions. I think Phil was more of an actor than a comedian." Film critic Pauline Kael declared that "Phil Hartman and Jan Hooks on Saturday Night Live are two of the best comic actors I've ever seen."  Writer and acting coach Paul Ryan noted Hartman's work ethic with his impressions. He assembled a collection of video footage of the figure he was preparing to impersonate and watched this continually until he "completely embodied the person". Ryan concluded that "what made [Hartman's impressions] so funny and spot on was Phil's ability to add that perfect touch that only comes from trial and error and practicing in front of audiences and fellow actors." Hartman described this process as "technical." Journalist Lyle V. Harris said Hartman showed a "rare talent for morphing into [...] anybody he wanted to be".  Ken Tucker summarized Hartman's comedic style: "He could momentarily fool audiences into thinking he was the straight man, but then he'd cock an eyebrow and give his voice an ironic lilt that delivered a punchline like a fast slider--you barely saw it coming until you started laughing." Hartman claimed that he borrowed his style from actor Bill Murray: "He's been a great influence on me - when he did that smarmy thing in Ghostbusters, then the same sort of thing in Groundhog Day. I tried to imitate it. I couldn't. I wasn't good enough. But I discovered an element of something else, so in a sick kind of way I made myself a career by doing a bad imitation of another comic."

Was he straight?
but then he'd cock an eyebrow and give his voice an ironic lilt that delivered a punchline like a fast slider--you barely saw it coming until you started laughing."