The answer to 'grass brown patches' is that there are several common causes, including drought, disease, pests, and improper mowing or watering. Brown patches can be caused by fungal diseases like brown patch or dollar spot, insect damage from grubs or chinch bugs, or simply not providing the right amount of water and nutrients for your lawn.
If the brown patches are isolated and cover a small area, you may be able to address the issue yourself through proper lawn care practices like aerating, overseeding, and applying the right fertilizer or fungicide. However, if the problem is widespread or you're unsure of the cause, it's best to call in a professional landscaper or lawn care specialist to diagnose and treat the issue properly.