A teraflop is a rate of computing speed that achieves one trillion floating point operations per second. "Flops" refer to "floating point operations per second." The floating point method is similar to scientific notation and uses an exponent to scale real numbers and support a wider range of values than the alternative fixed-point method.
Techopedia explains Teraflop
In practical use, a teraflop valuation would be generated by calculations that take the peak processing power of a single processor and the clock speed of each processor to estimate total peak computing power for a device. While the gigaflop remains the standard in measuring computing power, tech experts have begun talking about a teraflop in new technologies currently in development, including Intel’s Knight’s Corner machine - planned for 2013. Currently, the teraflop is not achievable with today’s consumer devices, and experts refer to teraflop-able devices, which use multi-core technology to generate these extremely high processing speeds, as "breaking the barrier" of the race toward much faster devices.