Oh - the inlines load from the muzzle for sure - loose powder and bullet - then usually a shotshell primer in a holder that the firing pin in the bolt hits. That's for the bolt actioned inlines. In the ones with hammers, the hammer usually hits a firing pin that hits the primer.
Most use a plastic cupped (sabot), copper jacketed bullet.
Some guys shooot full sized bullets, most don't.
Most inlines have difficulty loading the next shot without wip[ing the bore - some are impossible to load without doing that, while some allow shooting 2, maybe even 3 shots before wiping is necessary. Of course, none of them acually leave a lubricant in the bore to soften fouling shot to shot, so fouling continues to build, changing the interior of the bore for each successive shot, which effects accuracy in a negative way - usually.
Some inlines can also smokeles powders while most don't advise it. The odd smokeless powder inline shooting smokeless powder blows into tiny pieces. DOH!