So I need help understanding how avalible xp and total xp work.

Available is available to spend. Total is how much they have acquired over the game.

I'm sorry but I still don't quite understand.

Total XP is how much any one PC has earned over the entire course of the game. It's a rough way to track which "level" a character or group is. In four session, if a PC has gained 60 XP, they count their total as 60 XP (or 60 + Starting if that's how you want).

Available is how much XP any one PC has that they can spend on skills and talents. It is however much XP you have not yet spent.

If I am a human with a starting XP of 110, and I spend all of that at character creation, then after the first session I was awarded 20 additional XP but I have not spent that XP yet, I have 130 total XP, but only 20 of it is available to spend because the 110 was already spent at character creation.

Next, I decide to spend 15 of that on skill ranks. I still have 130XP total, but only 5 left available to spend.

It helps to not think of that XP as gone, but no longer available to spend, because it has already been spent.

As you play the game and advance the story, you will be awarded with Experience Points. The total you have accrued over the lifespan of your character is the Total XP.

To advance your character, increasing skills, adding talents, specializations and possibly force powers, you must "buy" them with experience points. Available XP is the amount of XP you have earned that hasn't been applied to the purchase of something yet.

Thanks.