side effects - seems to depend on each person. Some have no problems at all, some say they gain weight on it. there are many different ones, some women have problems with one but change to another and are fine.
there is an increased risk of dvt so your dr may ask you about other risk factors - obesity, family hx of clots, blood pressure, smoking. i think you aren't recommended to have it if you have family hx of breast cancer.

it is an effective birth control ?98/99% effective if you take it religiously and be careful if you have diarrhea.
you can also skip the sugar pills if you don't want a period every month.
if you decide it is time to have kids, you become fertile again within a short time, unlike some other methods that can take a long time.

can be helpful for acne and menstrual cramping if that is an issue

generally regarded as a good form of contraception for women in stable relationships. if you aren't in a stable relationship you must use condoms as the pill doesn't prevent the spread of STDs