Stan, its a secret code like SCTA car designations. TTR is a late model Yamaha trail bike. 125 is a small displacement one and the 230's are more popular. The picture shows one.
The TTR's used to be the bottom of the line for Yamaha dirt bikes. The big four plus Husky and KTM got into a dirt bike arms race. The bikes got real tall with seats far off of the ground. More suspension travel that way. They went to water cooling and fuel injection. Don't ask me why. Then, to get power, they went to dual overhead cams with shims and buckets and extremely over square engines. The bikes make power but they are hard to ride, very expensive to maintain, and they need much more frequent rebuilds.
There are plenty of dirt bikes out there for long legged twenty and thirty something guys full of testosterone. Everyone else makes do with bikes like the TTR's. They are top of the line for a lot of folks. They are good bikes and parts are available and reasonably priced. Now, if we had some more details about this one.