"There's a snake in our yard!"
There are 32 species of snakes native to Tennessee, so eventually you will probably see one of these in your yard. Snakes will always follow their food source, such as rats, mice, lizards, frogs, etc. If you have a rodent problem, sooner or later you will have a snake problem.
However, if your yard is neat with trees trimmed and bushes cut back with no signs of vermin, the snake you see is very likely searching for a food source. If he finds nothing in your yard, he will simply cross your property and keep looking. After all, this is how snakes look for food.
But if you do have a rodent problem, a snake just might look for shelter on your property such as an attic or crawl space, or even debris such as bricks or wood. When a snake has found a good food source, he won't be in a hurry to move on. And that can be a problem.