Are women and men truly equal in capacity. If so, why is the gap so big, in terms of salaries and positions?

No, we are physically and mentally different, although I don't believe that this is an excuse for differing rates of pay or discrimination.
Absolute equality between us will never be a realistic proposition unless we somehow mutate into an androgynous, hermaphroditic species of clones.
The closest we'll ever get is an acceptance and recognition of the differences between us, and how each person can contribute with their own particular set of skills.

I read an article concerning this very question, and it explained it like this.

If you take a male and a female, and they both finish college, and have the same degree, in 10 years, the man will make more than the women why:

seems that most "career" women don't work as long or as hard and a "career" guy. it said the average women will stop working for 2 to 5 years in a 15 year period to have a family or raise children, meanwhile the guy is still working the job and earning promotions. so on paper it may seem like she is underpaid, but the fact is he has just worked longer at the same job then the female and has earned more or better promotions.

What gap? I saw a study showing that women, ages 18-34, who worked made more money than men.

Because not everyone is willing to do the tough jobs.

Yes, man and women are equal in capacity. The difference is almost entirely due to children: women take time off for children, have career breaks for them, and choose jobs with child-friendly hours. Men do not, and get promotion because of it.

Recent research showed that that, while women on average earn only about 75-80% of what men do, single women with no children in the US earn 99% of what men do - effectively the same. At the other end, single mothers earn about 50% of what men do. Women sacrifice career for children.

no they are not but they should be treated equally.

"if men and women are supposed to be equal, why do people say its bad for a man to hit a woman?" - men and women will never truly be treated equally.

men and women all have great opinions and skills to offer. no one is the same. some women have greater skills than men, some men have greater skills than women. these things differ from person to person. some things can and will change, some things will remain the same.

Its not in the intellect that lie the differences, Its their social behavior. Men get together and form independent groups against women's competition as a self defense mechanism and/or repressed homosexuality (I have a theory about machism and homosexuality, but it would take too long). Women don't do that because they prefer being in mixed groups and never get along between themselves. So professionally, you end up with lots of all male groups, very few mixed groups (cause men don't want them) and some all female groups where people are there not because they want to but because they can't get into the all male groups, and they are not very successful. That's the reason why feminism never really worked very well too, all female groups don't work very well.

That's my opinion from my own observation of the world.