What do the dextro and levo prefixes mean in latin?

The prefix dextro comes from the Latin word dexter. It means on the right side or to the right.
The prefix levo comes from the Latin word laevo. It means on the left side or to the left.
We see these terms when we talk about chiral molecules rotating the plane of polarized light.
If the plane of polarized light is rotated clockwise as it approaches the observer (to the right if you are steering a car) the molecule is dextrorotatory (d).
If the plane of polarized light is rotated counterclockwise (to the left) the molecule is levorotatory (l).
We also see the terms dextro and levo when talking about sugars.
For example glucose exists as D-glucose and L-glucose.
Here the D and L do not refer to the direction of rotation of polarized light. Instead they refer to the Fischer projections.
If the OH in the highest-numbered chiral carbon (closest to the bottom) is on the right we have a D-sugar. If the OH is on the left we have an L-sugar.