WHAT'S A superstar?
Answer: Frank Sinatra.
* Why has he lasted this long? Who would pay $50 to see him in concert?
Well, there's the talent. The voice isn't what it was, but there is enough left for the people who grew up on him. They don't wear bobby sox and scream themselves hoarse, but they truly, deeply, love the man, probably because he is a reminder of their youth. Men and women in their 50s, 60s and 70s remember smooching to the Sinatra hits.
* How old is he?
He was born Dec. 12, 1915, in Hoboken, N.J. He's 75.
* Scrappy, isn't he?
From the beginning. Over the years he has had fights with members of the press. He used his fists on columnist Lee Mortimer and would like to have given the same treatment to Westbrook Pegler, another columnist, a true Sinatra hater.
* Did any of this hurt him?
Not really. Despite his public and private behavior, his fans go on adoring him.
* Was he always big?
No. There was a time, in the early '50s when his movie and recording careers failed. That was when he begged Harry Cohn, president of Columbia Pictures, to cast him as Maggio in ''From Here to Eternity.'' Cohn wanted Eli Wallach, but Wallach was busy, so Cohn agreed to give the role to Sinatra, who agreed to do it for $8,000, a piddling sum, even in those days.
* How did the Sinatra career begin?
It started when he was 19. He was part of a song group that won attention on the Major Bowes Amateur Hour. He toured with Major Bowes shows for three months, then returned to Hoboken where he sang at the Rustic Cabin for $15 a week.
* Did someone discover him there?
Harry James, who asked him to sing with the James band. He made his first recordings with James. One was ''All or Nothing At All,'' one of Sinatra's signature songs.
Then it was Tommy Dorsey for a time.
Then, in 1942, Sinatra told Dorsey he wanted to work on his own. Dorsey let him go with the provision that he share in Sinatra's future earnings.
* When did he do his first film?
He did three low-budget cameos in the early '40s, then, in 1943, he appeared at New York's Paramount Theater.
* Is that when all the screaming began?
That's when the teen-agers, in bobby socks, began to scream their lungs dry. Some historians say all this was staged by a clever press agent. Others say it was spontaneous, a roar whose time had come. One shrink said it was mob hysteria that was probably the result of greater knowledge, pertaining to sex, among the young. Whatever, Sinatra continued at the Paramount for eight weeks, and the screaming never stopped.
* When did he do his first first starring role in films?
That was 1943. The movie was ''Higher and Higher,'' and the girl who gave him his first screen kiss was Barbara Hale of the ''Perry Mason'' series.
* How many films did he do with Gene Kelly?
Three, ''Anchors Aweigh,'' ''Take Me Out to the Ball Game'' and ''On the Town.''
* Then what happened?
In 1951, he did two low-budget films, and his movie career died. So did the recording career. It was at this time that Sinatra did things like ''Too Old to Cut the Mustard'' with Marlene Dietrich. He also did a recording with Dagmar, a big-busted blond who won some notoriety on the ''Tonight Show'' before Johnny Carson took over.
* And his private life?
That was in shambles, too. He had divorced his first wife, Nancy Barbato, and married Ava Gardner, a stormy association that lasted little more than two years. Later, he would marry Mia Farrow, divorce her and marry Barbara Marx, widow of Zeppo Marx, one of the Marx Brothers. This union has lasted longer than all the others.
* Didn't he retire at one time?
Yes, that was in 1971 when he made his ''final'' appearance at the age of 55 at the Los Angeles Music Center.
* How long did that last?
* What was the ''Rat Pack?''
It was a group led by Sinatra, and it included Peter Lawford, Sammy Davis Jr., Joey Bishop and Dean Martin. They did a number of films together, ''Ocean's Eleven,'' ''Sergeants 3'' and ''Robin and the Seven Hoods.''
* What's he been doing lately?
He toured with some of his ''Rat Pack'' friends, Sammy Davis Jr. and Dean Martin. Martin withdrew and was replaced by Liza Minnelli, who was the first to sing ''New York, New York'' (in the 1977 film of that title), another Sinatra signature. Davis died some time after the tour.
Frank Sinatra is scheduled to perform Monday at 7:30 p.m. at Merriweather Post Pavilion. Seating tickets are $50 and lawn tickets $19.50. For tickets, call 1-800-448-9009.