Classes
All 10 core classes in the D&D game underwent at least minor revisions to balance the classes and make some classes more useful. The bard class receives additional skill points and has access to more spells at each level in 3.5, while the animal companion of the Druid class now increases in strength over time. Rangers in 3.5 are reduced to a d8 hit die, and must choose between long range and two-weapon fighting specialization, rather than having both.
Skills
While skills continue to behave in the same way as they did in 3.0, several of the skills in version 3.5 have been combined or removed. The "innuendo" skill no longer exists in 3.5 and is instead included as part of the "bluff" skill. Likewise, the "intuit direction" skill is removed and is instead part of the "survival" skill. The "knowledge (dungeoneering)" skill is added in 3.5, which lets characters recall information about creatures or locations in specific dungeons.
Feats
In version 3.5, feats continue to give characters and non-player characters (NPCs) access to additional abilities and bonuses beyond what they receive from their class. Version 3.5 streamlines the feat selection so that certain feats always provide +2 skill bonus, such as the "stealthy" feat providing a bonus to the "hide" and "move silently" skills. NPCs also receive feats at the same rate as characters in 3.5, gaining one feat for every three hit dice the creature possesses.
Spells
Spells available to the spell casting classes undergo various changes in 3.5 to balance the classes and prevent certain overpowered spell effects from being abused. While the "heal" spell restored all hit point damage in 3.0, it instead only heals 10 points of damage per level in 3.5. Many spells are also combined together, such as the "symbol of fear," "symbol of persuasion" and "symbol of stunning" spells being rolled into a single spell.