How do skill points work?

[NecroDancer]

I'm new to 3.5 and the skill system makes no sense to me, can someone please exsplain how the skill system work?

(Sorry for bad grammer or misspells, I'm using mobile).

[digiman619]

Skills represent how skilled you are in certain tasks. For the purpose of this explanation, let's focus on the Swim skill. Part of swimming you simply your muscles, represented here by your Strength stat. But muscle isn't everything; there's also technique. This is where skill points come into play. Skill points are how you "practice" your skills; if you spend your downtime practicing the piano over hitting the pool, you'll be a better pianist than a swimmer. The maximum number of ranks you can invest in a skill in 3.5 is 3 + your level; you're not going to be a better clockmaker right off the bat than someone who has been doing it for decades.

Once you've have your skill points set, now we get to the checks. The Difficulty Class or DC is the number that you have to meet to succeed at a given task. It's far easier to swim with the current than against it. To make a skill check, you need to roll a d20 (that funky 20 sided die) and add that number to your ranks in the skill plus your base ability (for Swim it's Strength) plus any other modifiers both for and against. If that number is greater than or equal to the DC, you succeed. If it 's lesser, you fail. Some skills have consequences for failing or failing by too much; look at each skill entry for details.

[A_S]

digiman619's overview above is spot-on for how using skills works, but a little more on how you obtain skills is probably in order.

Every time you gain a level (including your first level), you gain Skill Points, which you must spend on ranks in your skills. The number of skill points you gain in a given level depends on: What class you're taking that level (Fighters (http://www.d20srd.org/srd/classes/fighter.htm) get 2 skill points/level, Rogues (http://www.d20srd.org/srd/classes/rogue.htm) get 8)
Your Intelligence bonus
Other stuff (Humans get an extra 1 skill point/level
At character level 1, you get four times as many skill points as normal
So, a level 1 Human Fighter with 12 Intelligence would start the game with 16 skill points (2 for Fighter, 1 for +1 Int bonus, 1 for being human, and times 4 for it being 1st level). Since, as digiman619 points out above, the maximum number of ranks you can put into a skill is (character level +3), she might start the game with 4 ranks in Balance, 4 ranks in Ride, 4 ranks in Intimidate, and 4 rank in Craft (weaponsmith).

Class Skills: The fighter in the example above was able to buy skill ranks for 1 point apiece because all the skills she took are Class Skills for a Fighter. However, if she wanted to start the game with ranks in Tumble, she would have had to take it as a Cross-class Skill, because Tumble isn't on the Fighter's class skill list. When purchasing cross-class skills, each skill point you spend only buys you half a skill rank, so if she'd put 4 of her skill points into Tumble instead of Ride, she'd only have started the game with 2 ranks in Tumble.

The maximum number of ranks you can have in a cross-class skill is normally half the maximum for a class skill. However, any skill which has ever been a class skill for your character is always considered a class skill for the purpose of the maximum number of ranks you can put into it. If the Fighter in the example above took a level in Wizard upon becoming a second level character, and became a Fighter 1/Wizard 1, she could still increase her Intimidate skill to 5, she'd just have to spend 2 skill points to do so (because Intimidate is a cross-class skill for Wizards).

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As you may have noticed, this system is a confusing mess! It's simple enough for single-classed characters, but if you're multiclassing, there can be some very counter-intuitive optimization strategies involving making sure you only buy skills when leveling in classes that have those skills on their class list. This is why Pathfinder simplified the system considerably.

You've probably already seen these pages, but the rules for skills in 3.5 are spelled out here (http://www.d20srd.org/srd/skills/skillsSummary.htm) and here (http://www.d20srd.org/srd/skills/usingSkills.htm)

[NecroDancer]

Thanks this makes a lot of sense