what is F1 strains and what is S1 ?

some weapons-grade passive aggression from organoman Bwahah. These are terms related to mendellian inheritance. They come from the 1800s. It's not a matter opinion or preference. He just doesn't like that i shit on the absolutely meaningless marketing term "organic" and call out urban myths like blind defoliation and flushing before harvest to magically make the buds taste better despite having no impact on what constitutes those buds in a measureable way.

Papa_T has given you the correct answer.

F1 is a science term, think s1 is less official like a few terms you'll see on "ethos" that sounds science-y but is not. F1 is the first filial generation. You could think of it as the start of a family tree. Rather arbitrary where you start. S1 means it's the first generation produced from a selfed plant. There are some other made up ones like R1 or Rbx etc. these are more like model numbers than real science terms. I'm not a fan of selfed seeds. Even lower chance you find a plant that checks all the boxes fromt taste to yield to potency. the marijuana plant is quite sensitive to inbreeding, unlike some other types of plants. Even 1 generation has a noticeable impact. Last one i tried was grandpa's stash R1 and it was okay but also one of the worst plants of all that i grew last year. It was a "6" standing next to "8-9-10's" lol. And consitently, some amatuer F1s i made outpace and are frostier than the inbred shit. https://en.wikipedia.org/wiki/Mendelian_inheritance https://biologydictionary.net/f1-generation/

An F1 strain is the first offspring of two different phenotypes that have been bred together. S1 is the offspring of a feminized plant that was self pollinated to make seeds.