Television shows are made by various production companies. Then these shows are sold via various ways.
One way is via national over the air (OTA) networks. Think of “The Big Bang Theory.”
Now some shows like “Oprah” aren’t on a network. “The Big Bang Theory,” airs on CBS, but “Oprah” can air on any TV station, ABC, NBC, CBS or Independent.
This is what, as another poster noted is called “First Run Syndication.” In the 80s we had a glut of first run syndication. “It’s A Living,” “Too Close For Comfort,” “Charles In Charles,” and “Mama’s Family,” were among the shows that started out on a network, to cancelled and instead of going away, they made NEW episodes and put them into first run syndication. You also had shows like “Small Wonder” and “Xena” which never ran on a network. They were always first run syndication.
Show as another poster noted, like to have 100 episodes 'cause that makes it easier to syndicate. However there were exceptions. “The Honeymooners” only made 39 episodes and these were syndicated and were very popular. “The Honeymooners” was a bit odd 'cause it aired as its own show(39 episodes) and it also aired as just one sketch on “The Jackie Glenson Show.” Later on the episodes that aired as part of the “Jackie Gleason Show,” were found and added to that package.
Remember back in the 50s and early to mid 60s, TV shows made 39 new episodes a season. Then it was slowly reduced over the year to 36, them 33, then 29, then 26, now most TV shows have 22 or 23 new episodes a year. So a show like “Gilligan’s Island” ran only three years but had 98 episodes. Now it would take more than four years to get that many episodes.
When a show gets to a hundred episodes or has been on the air for four years, it gets sold into syndication. How it’s sold is a matter of popularity.
Hugly popular shows like “Seinfeld” were sold with exclusitivity. That means originally “Seinfeld” ran on one TV station per market. It wasn’t allowed to run on cable. Why? Because that’s too much exposure. Later on after the original syndication contract was up, “Seinfeld” was allowed to run on one station per market AND a cable channel"
Some shows are not as successful. This show was sold right from the start to BOTH cable and OTA TV markets. Such as “Still Standing”
Some shows like “Ellen,” (sitcom) and “Dave’s World” were sold directly into cable with no local OTA markets.
Who controls the order the shows are shown? It depends on the show being syndicated. Some shows are sold and the production company controls the order. Some do not. Some shows are also sold, with conditions like, “must be played twice each weekday,” or other conditons.
In the old days TV shows were usually syndicated after they ran for seven years, not four. Many areas of the United States didn’t have cable (this was in the late 70s) and didn’t have all three major networks ABC, NBC, and CBS. (FOX and the CW didn’t exist
So not all areas of the USA got to see all TV shows when they were first run. This is why often a show went into syndication it changed it name. This way the TV station showig it couldn’t pass it off as a first run TV show.
“Bonanza” became “Ponderosa”
“Happy Days” became “Happy Days Again”
“Carol Burnett” became “Carol Burnett And Friends”
“Laverne and Shirley” became “Laverne and Shirley and Company”
“The Andy Griffith Show” became “Andy of Mayberry.”
This way viewers could be sure they were seeing reruns not first run shows.