SE, SLE, SLT, What's the difference?

I have a 97 serria SLT. I have noticed other trucks with SE, or SLE badges on them. Since I bought the truck used, I dont know what the differences are between these. Does anybody know what they are???

That is the model designation, usually designates trim levels
SE is the base model..usually no frills
SLE is the mid range..power accessories are standard
SLT upper range..leather and all the goodies