I'm watching LOST and im so confused. I need some answers n such.?

ok so i was watching it intensely for a month and got to season 5 almost to the end. and then i stopped for a bit and i started watching it again. So im confused because that time travel crap that happened. Like sawyer kate juliet jack hurly etc.. r all in 1 time zone or era, back when the dharma initiative still occupied the island. John and Richard and Ben are in another time era? Also i just finished an episode were when sayid is shot and they are going to the swan station and then sawyer kate and juliet are back on the island. Im so confused can any1 please explain to me wth is going on. I understood fine untill the time travel thing occured. if you can go through a quick explanation or something i would really appretiate it