Question, The First
I am trying to determine my character's Hit Points.
A character or creature gains maximum hit points at 1st level or if its first Hit Die roll is for a character class level.
Ok, so I'm a level one Gnome Monk therefore my HP initially is d8 (or is it simply the value "8")?Also, what is meant by "or if its first Hit Die roll is for a character class level".?
Question, The Second
Let's say that through a combination of luck and hard work I advance to the next level. How do I then calculate my HP? The following explanation defies my interpretive abilities~
To determine a character or creature's hit points for levels beyond 1st, roll the dice indicated by its Hit Dice. Creatures whose first Hit Die comes from an NPC class or from his race roll their first Hit Die normally.
Ok, so the first step is "roll the dice indicated by its Hit Dice". What is my Hit Dice? And what does "Creatures whose firs Hit Die comes from an NPC class or from his race roll their first Hit Die normally." mean?
Your gnome monk starts with 8 hp. Add to that whatever his Constitution bonus is. The quick way to get the binus is (Score/2)-5, or check the table.
Favored class can also increase your HP, optionally, as can feats like Toughness.
At next level, you will roll 1d8+Con bonus and add that to your total.
1: Your Gnome Monk's hit points would be 8, plus any bonuses from a high Constitution score or from your favored class bonus.
1b: See answer to 2b.
2: You roll a die that matches your class' stated HD-type. As you noted above, Monks get a "d8" HD, so you would roll an 8-sided die.
2b: That means that characters whose first level was one of the NPC classes (Adept, Commoner, Expert, Warrior) don't get maximum hit points for their first level. It also means that Bestiary creatures who have a number of HD already indicated in their statblock don't get maximum hit points for their first level.
The second part of the first quote is answered in the second quote. It is for NPC classed creatures (Warriors, Experts, Commoners, etc.) or monsters that roll for the 1st hit-dice hit-points, but get the full hit-dice when they take fighter 1.
For the second part, your monk says "Hit Dice: d8". When you hit level 2, you roll your d8 dice and add that value to your new base hit-points.
Gnome Monk with 17 Constitution (+3 bonus)
Level 1: 8+3HP = 11HP
Level 2, rolls a 3 on the d8: (8+3)+(3*2) = 17HP
Level 3, rolls a 6 on the d8: (8+3+6)+(3*3) = 26HP
Level 4, Add your Ability Increase to CON (now at 18), rolls a 4: (8+3+6+4)+(4*4) = 37HP
Plenty of good answers here, so I won't bother repeating them all. It sounds to me like there's simply an issue with the terminology used in the game. Give it some time, you'll get used to it. :)
archmagi1 touches on something here as well that's worth paying attention to:
If your Constitution Bonus increases, you will immediately and retroactively increase your hit points. To use his example:
17 Constitution (+3 Bonus)
Level 1 - You gain maximum for your 1st Level Hit Die, plus your CON bonus (+3), so 11hp.
If someone casts a spell on you that grants you +4 Constitution, you will get an additional +2 Bonus from your Constitution, so your Hit Points will temporarily increase to:
8 + 3 + 2 = 13
Similarly, if you take Constitution "damage" (via poisons or spells or what-have-you), this can and will decrease your characters Hit Points.
A good rule of thumb (and in fact exactly the rules) is that for every 2 points of Constitution (determined on the even number of the pair), you either gain or lose 1 HP.
So if you go from the 10-11 pair to the 12-13 pair you gain +1 CON modifier, which gives you +1 HP/Level as well as increasing your CON based abilities, such as Fortitude Save.
Likewise, if you go from the 10-11 pair to the 8-9 pair, you will decrease those values.
It's a bit of book keeping, but it does help to emulate your characters overall physical hardiness being impacted both positively and negatively by environmental factors that aren't weapons tearing up its flesh.
You might also want to speak to your GM to find out if you will be rolling for hp beyond first level. Many GMs (myself included) prefer PCs take average hp (1/2 rounded down on even levels, 1/2 rounded up at odd) instead of rolling.
In theory, the rules state (somewhere?) that any PC class (i.e. not an NPC class or monster HD) gets the highest roll on its hit die at 1st level. This means that Brotato's version is a "house rule" but his point is solid, you should check with your GM on the HP issue. There are a LOT of groups with HP generation house rules!