what exactly it's called

Question first then back ground in case it's relevant;Six months in with tubeless and losing air.... I'm told to get a 'shot' or small portion of Stan's to add through the valve after removing the core. *Please advise by. Any tips related to that process very appreciated also.My bike has been tubeless for about 6 months and all I know about that is the guy who set it up this way. I rode pretty regularly up to about two months ago so the bike sat for a while.Just this week, I'm experiencing my first loss of air and thus far, it seems the front won't hold it very long. Sunday, we biked about 2 hours and it felt soft part way through the ride. By 3/4 of that ride, I added air to get back to the car. I pumped it up at home and spun the wheel some as suggested by him (better yet ride it some) but that, I did not. Still not holding air.I heard all the great benefits and believed most of what I'd heard but it just didn't grab me by the shirt tails and I was happily pushing pedal, not feeling lost out.Eventually, a friend who'd been harping on and on about converting my bike over to tubeless got to me and I felt I'd hurt his feeling arguing otherwise. Beers and music later, it was done. This was likely 6 months ago. It all worked well, held up fine and I barely had to add air in that time. I was more impressed by the job he did than tubeless itself. I thought had read even the best of situations can still mean a bit of TLC or potential for being finicky. Maybe ?Anyways--- As you might guess, I didn't go to school on tubeless conversion, didn't really get to know the process, or doctor up the ingredients or kit involved etc Most of my reasoning for being too lazy about going that route prior was to keep biking simple and fun. I'm not really a 'wrench' and stick to the basics and minimums of caring for the bike and keeping it rolling healthy.I know John will fix me up if needed but I want to follow his advice and start to learn as I go on this tubeless adventure. The benefits make sense and as long as it doesn't outweigh itself by being more problematic than it's worth (in my world), I'll stick with it and learn more in time.I'll admit I appreciate those handy with bike repairs, big tear downs or bike builds, buying special groceries to whip up homemade chain lube etc.... it's just a little bit Deep Woods for me and as per time available at present.Thanks in advance for anything representing simple advice, steps and the right stuff to purchase.~b