When you are working on your airplane's engine or just inspecting it to make sure that it's in good shape after a certain amount of flight hours, it isn't all that easy to look at the entire engine and see what is going on inside. It's not like your car engine that you could take apart and put back together again to look inside and see any problems. For one thing, your car's engine is a lot smaller than airplane's engine, and taking apart your airplane's engine if you don't have to requires a lot of time and a lot of space, especially you generally can't easily take an engine out of your airplane. There are ways that you can take a look at what is going on in your engine.
A borescope is a long, flexible cable that is usually made up of fiber optics. It generally has a light and a camera on one end. You can feed the cable into your engine and send it around corners, bends, and into various cylinders. The light will make sure that the camera has enough light for you to see what is going on in your engine. The camera sends back an image so that you can see what's going on and where you are sending the camera. There are several benefits to using a borescope to inspect your engine.
One benefit is that a borescope will do no damage to your engine. That's because they are generally covered in a rubberized material. It's a tough material so that it can protect the fiber optics, but flexible enough that it will flex and bend around all the bends. Another benefit is that it is going to save you a lot of time. If all you need to do to figure out if your engine is alright is to send a borescope through it to look at it rather than guess and take your engine apart only to put it back together again without finding a problem, you are going to save a lot of man hours and get you back up in the air sooner.
Your airplane's engine should be checked out every so often, just to make sure that it's working as it should. You don't want to be thousands of feet in the air only to have your engine fail on you. A borescope can help you with that.