I can give you the perspective of someone who has just gone through the process in the US; the North American system is a little different from that utilized elsewhere in the world so please do keep that in mind.

In the US, undergraduate education lasts four years. You will make History a major concentration, meaning it will constitute about a third to half of your required classwork (the US, uniquely, requires that students in University receive a broad liberal arts training). Most of these classes will be lecture based, meaning you will sit in a room and listen to a professor run through the material, and will cover a broad geographic, temporal, or thematic subject (Modern Japan, Ancient India, US Labor, etc). You will likely read at least five solid books and a number of smaller articles. Some classes, however, will be smaller seminars in which you hone in on a more focused subject, often something within a professor's area of research interest. In all of your coursework, you will do some serious writing, often a term paper of at least 15 pages arguing for or against a particular historical perspective.

If you plan on matriculating to graduate work, there are some other things you really should do while an undergraduate. First, learn a language, or preferably two--especially if you want to work on a region outside of your home country. Second, write a senior thesis. It will give you a taste of what research toward a longer project looks like, and might even get you into some archives here and there. Together, the thesis and language skills will make you a much more competitive candidate for grad school.

Grad school is a very different kettle of fish. Your first two years or so will be spent on coursework, in this case entirely comprised of seminars in which you read serious amounts of secondary literature with a half-dozen to a dozen other graduate students. These are designed to get you acquainted with the discussions that comprise the field--what are the historiographic squabbles? What are the hot topics? Next, you will taker you comprehensive exams, during which you will be tested in three or so broad areas on the basis of reading lists comprised of literally hundreds of books and articles. Once you passed, you'll be rewarded with a meaningless masters degree which is essentially just a gold star.

Now the real work begins. You will, working with an adviser and a few other faculty, choose a very specific research problem and devote the next three plus years of your life to a three-hundred page dissertation solving it. You will likely spend a year in archives, often away from home. You will then spend a year or two writing a thousand words a day. It can be a very lonely, but very rewarding life.

Throughout it all, you will need to publish, and also get some teaching experience (usually as a teaching assistant grading papers or leading discussion sections for a professors' lecture course).

Then you finally write the last word of the dissertation and are ready to defend it in front of a committee of three or more experts in your field. Don't worry, you'll pass, your adviser won't let you go through this rite of passage until your ready.

So, congrats! You've passed! All told, you will now have spent an entire decade or more in post-secondary school. What now? The job market of course! The thing is, being a professor is hard but great fun and still at least moderately respected. A lot of people want to do it, and the graduate schools push out a lot more graduates than the market can absorb. So for every job for which you are applying, there will be an army of other recent PhDs to contend with. Half of them will never make it into the academy. OF those who do, many will find themselves without tenure, the traditional path to a professorship that for generations afforded scholars with real protections and job security. Instead, chances are you'll be "adjuncting", teaching classes ona contract basis for low pay and no benefits, with no job security. But hey, people will call you "doctor," so that's cool.

I tell you that not to dissuade you, but to give you an accurate sense of what you're in for. By all means, go for it! I just advise you to only do it if you aren't paying for it. In the US, undergrad + grad without fellowships could cost as much as half a million dollars. It is not worth that. Work hard and apply for scholarships and funded PhD programs, and let those enowment-rich universities pick up the tab. Think of it as a job, one that might not lead to riches down the road, but one that will let you spend a decade reading interesting books, meeting interesting people, traveling to interesting places, and working on interesting research. If it leads to something, then that's just gravy. If not, you just start your life at 32 instead of 22, at a real economic disadvantage, but rich in invaluable experiences.