Logic level translation refers to the communication between logical devices within a system.  In modern electronics, it is often the case that these devices operate on different voltage rails or levels.  This is especially true in modern CMOS devices, which continue to decrease in size, and thus requires lower voltages.  When these circuits need to communicate with circuits that operate at a different voltage level, a logic translator is used.

Many factors must be accounted for when translating voltages.  Modern devices run at very high frequencies, and there are inherent parasitic capacitances involved in translation.  Often logic voltage shifts cannot operate at the same speed as the individual circuits they are translating for.  This is especially true of up shifting, or raising the voltage from high to low, which is much more difficult and lossy than dropping the voltage.

In computers, the three main voltages rails used today are 5V, 3.3V, and 1.8V.  Many translators exist to convert between these levels.  Some even allow for bi-directional conversion, which can upshift and downshift within the same general circuit.  Usually component-wise, the translation circuits are designed from resistive capacitive or resistive transistor networks, or a combination of both.