When you get into FF sensors, you will get a much shallower depth of field than with a small sensor camera. With a point and shoot camera, for example, almost everything tends to be in focus. That makes them easy to use and get sharp in-focus shots.
With a FF DSLR, photographers use the ability to have a shallow depth of field to isolate a subject and have things in the background be out of focus.
However, there are times when you want as much as possible to be in focus, landscapes, or groups of people. In cases like this, you must use small apertures, f/8, f/11, even f/16.
Setup your camera and take several shots focusing on something fairly close with a few different apertures and you will see the difference in background focus.
Then, step back a ways and do the same thing. Notice that the depth of field is greater when you are back from your subject.
Use a combination of these techniques to control what is in focus.