Example of wide open aperture. this was shot at about f2.8. Notice how my dog is in sharp focus but the background is blown out? the fuzzy area is called bokeh.
In macro type shots the focal plane tightens up to almost a razor thin area that is in sharp focus. increasing the f# will close the aperture and give you better depth of focus but also lets less light in to the sensor.
You can compensate 2 ways. slow the shutter speed or increase ISO. increased ISO creates digital noise in your picture so if you want to keep quality up you have a longer exposure time. the problem with longer exposures when trying to hand hold is camera shake. anything longer than about 1/60th a second shutter speed and you will start to notice camera shake in your image. thats why a tripod is good.
Hopefully that wasnt too much. you'll get the hang of it pretty quick if you research a little and shoot in manual mode. also look up something called metering. that camera should do it and that will help a lot with finding the right exposure.
Good luck!!