Sounds like there's a problem with your lawn.

Need more information. Brown and burnt could be the same thing because burnt lawns look brown.

Where do you live?

What is your watering schedule? How often and for how long do you water?

How high/low do you mow?

When were the last two times you fertilized?

Have you applied any herbicide this year? If so, what and when?

Can you post a picture or two? One from the street and one from 3 inches away would be best. If you can take them when it is overcast or when the Sun is low in the sky that would be ideal. Pics taken in bright sunlight are almost always useless.