Obtainable Skills 101

Basics and Races
Obtainable skills are the building block of every character. The meaning behind the term is, that anyone can obtain them hence the name. However, some skills are harder to get for one reason or another. For example, an avian beastman would start with the flight skill, which is difficult for those who don't have wings to learn. Comparatively, a goblin would begin with the dexterity skill, which can be quickly learned by doing different tasks with your hands. It all depends on the skill itself and the player's race. In addition to that, some races get rare skills that can only be obtained by meeting certain conditions. As a rule of thumb, racial skills are harder to learn.
Classes
As I have hinted at, classes give skills as well. Depending on the class, you get specific skills pertaining to each class. For example, a barbarian will get the strong body skill vs a wizard who would get the magic aptitude skill. Besides starting skills, a class will have several skills that they will excel in while growing faster. Because of this, players can expand themselves and build their character based on these concepts. Races also give these kinds of benefits. One thing to note is players can get skills that are not related to their class and race. However, these skills do progress at a slower rate.
Races & Classes
When you mix your race and class, that's when your character is complete. Unfortunately, though, combing the two can prove tricky at times. Most of the time, your class takes priority over your race. To give an example, if you're playing orc wizard, you would still have the low defense of a wizard. In the opposite situation, if there were an elf barbarian, they would have good defenses, but they would be lower because they are elves. So while there is no "proper" way to play and freedom is encouraged, some classes and races naturally synergize.
Training & Choices
All skills start at level one and have a maximum of twenty. One exception to this rule is specialists. They have a cap of twenty-five for their respective skills. As obvious as it sounds, using your skills increases their level. However, there is a small clause with skills. How you use your skills will determine how they develop. For example, someone who uses Strong Body for strength and defensive purposes will change their skill differently than someone who trains the skill by purposely throwing themselves in danger. Meaning most skills will change to suit how someone plays, even if they mean it or not.
General Skills
Now for the big question, everyone's been wondering what skills are there and how many exist. To answer this question, we must look at our reality. ID Quest takes everyone's subconscious ideas and forms them into a world that people would like, including skills that appear in the world. So, you expect to see real-world skills and skills relating to fantasy. But to give some examples, there are skills relating to the body, magic, hobbies, and very obscure and niche skills. As you expect, some skills are more accessible than others, and some are more hidden than others. Look for and find what you want to use at the end of the day, and have fun playing the game.