Parallel thinking; simply being mindful of the area you're in, not some magic skill.
Sword Art; Sword Slash: Swinging a sword is not a skill, it's the intended use.
Gotta love authors who complicate things when there's no need to do so lol. Good to see Sora actually use his gun finally, and especially good to see that he can't just kill the horny orc with it.
As
@dragonlordadn said above skills are generally automatic actions based around a given thing. "Sword Skills" don't require him to have learned and practiced for years, but instead is able to use a sword "practically" and in combat simply by putting "points" into it.
Parallel Thinking, in terms of this manga, allows him to fully focus on two distinctly different things at the same time, without having the prerequisite mental capacity and training to do so.
The author isn't simply complaining things, if the author DIDN'T utilize this form of "skills" the MC wouldn't be able to use a sword unless he trained in it for years, which the author could arbitrarily skip over with a montage or simply saying that it happened, but he wouldn't have met the two girls and traveled with them, and any other "time" based things would have already ended. 'sides, who would he have found to teach him? How would he have paid them? He was forcibly removed from the castle and the town.