Sport betting is simply guessing the outcomes within or by the end of a sporting event and placing a wager on that outcome. It is important to note that 'outcome' in this context does not refer exclusively to scores or winning/losing the contest.

It may include events happening within the course of the contest e.g a player being sent off or an athlete dropping out of the race. It may also involve 'not-scores' (outcomes that are not likely to occur) like 'no headed goals scored' or 'no competitor to complete the race in under two hours.' It can also include a combination of outcomes.
Sports betting happens in virtually every sport, be it human controlled or unmanned animals. Soccer, American football, and basketball are among the most popular sports that punters place wagers on. Dog racing is arguably the most popular unmanned sport with sports bettors.
Who controls sport betting?
Bookmakers produce odds (probability stakes) which punters use to pick their favored teams and occurrences. Perceived weaker competitors often receive bigger odds from bookmakers in an attempt to lure people to place money on them.
Non-favorites don't often win but when they do they can yield astounding results. A popular example is a Leicester City fan who won £72,000 after betting on Leicester City winning the English Premier League in 2016. He would have had £178,000 more had he not cashed out weeks before the end of the league.
Is sport betting legal?
Largely yes. Bookmakers are licensed operators. There are, of course, some bookies operating illegally, but these are under the surface and largely unknown.
What are the popular wagers?
Most licensed bookmakers only accept money as the medium for placing bets and also for payout. Informal betting has however seen some very weird wagers including houses and cars.
Can't sports events be fixed?
This is a major problem that has dogged many sports disciplines as different circles try to influence outcomes to favor their bets. Sports organizers are always actively cracking down on this vice. Players are barred from betting in competitions where they take part,
The internet has revolutionized sports betting just as it has changed everything else. The rise of online gambling has opened up an enormous market for bookmakers. They no longer have to open physical premises for people to place bets or pick their payouts.
The safety of online gambling was a major concern for punters in its formative stages. It still remains so for people who are just getting into the sport. There dare definitely some scammers but there is no difference between placing bets online and going physically to a bookmaker. Just ensure you choose a licensed bookmaker.