Color can be tricky to understand because it is not inherently part of an object but instead depends on the human eye's ability to translate light into what the brain perceives as color. Brown in particular can be confusing since it's a composite color, and our perception of it is dependent on other factors. So when you are thinking about what colors make brown, the answer is: it depends.
The eye contains cone-shaped cells, which work with the attached nerves to translate short (blue), medium (green), and long wavelengths (red) of light into what is then perceived color by the human brain. The eye also possesses rod shaped cells, which process black and white light wavelengths. Nearly everything we see is not a pure color on the light spectrum, which is why we see as many colors as we do, and even see shades of commonly recognized colors.
When you think about seeing those not-pure colors, it makes sense to say that we will see a combination of yellow and red wavelengths as orange. We see brown when so many wavelengths are present that our brain can't interpret it as one color over another.
The light also affects the saturation, or how bright or dull the color is, and the lightness, or how light or dark it is, depending on what other wavelengths are present in smaller variations. This changes our perception so that we may see a different "shade" of brown.
You may have noticed that the easiest way to make the color brown is by mixing a bunch of other colors together and it's true that by doing this you do eventually do make brown.
Therefore, in order to make brown in painting, printing, and digital art, you need to combine colors. You can create brown from the primary colors red, yellow, and blue. Since red and yellow make orange, you can also make brown by mixing blue and orange. The RGB model used for creating color on screens like the television or a computer uses red and green to make brown.
The amount of each color combined can change the shade of brown, since this mimics the idea of saturation and lightness, and changes how we perceive the color. You can also add in more colors or change the proportions to change the shade, which we will go over later