Yes, that F means female. Naturally, if you see the letter M it means male. In most scenarios, it really doesn't matter about the gender. The only ones that would matter is if the mon in question is something like Vespiqueen or Salazzle or the weather genies where they're all gender locked
For the most part, the reason you see this is because of showdown. The teambuilder section of the thing has an option for you to export your Pokemon's set which essentially has a specific format with how the abilities, moves, whatever are written to make it easier to read. Clicking this option would also copy some random details like if that Pokemon is shiny or its gender which means that the player has set the Pokemon, in this case, Salamence, to female, whether they were aware of it or not
Of course, one can just manually type in a Pokemon's set in the exact same format as showdown's and if that's the case, chances are that person would forget the minor details like the mentioned gender or shiny. As I said, most of the time, gender doesn't matter at all since it's mostly just used for breeding. Sometimes it just comes down to personal preference because there are those that would prefer their entire team to be only male or only female mons even though it really doesn't matter
