Teraflops are Tera Floating-point operations per second. Floating-point operations per second is a measurement of the speed of a processor or of one of the arithmetic units of a processor. A floating point operation handles decimal numbers with decimal points coded using a certain number of bits.
The teraflops is a better unit for representing the calculating power of a processor than its frequency (in hertz, Hz), or the number of instructions per second which it is capable of executing (Mips, millions of instructions per second).
Prefixes are used : megaflops (106 flops), gigaflops (109), teraflops (1012) etc. Current processor speeds are generally measured in gigaflops.
The s is a part of the acronym and should therefore be kept in the singular : 1 teraflops, 1.5 teraflops. However, it is sometimes omitted: 1 teraflop, 1.5 teraflops, 2 teraflops.