Drishti is aspect — the influence a graha exerts on a place in the chart other than the one it occupies. Two things about the Jyotish version surprise people coming from Western astrology.
First, it counts whole [signs](/en/astrology/glossary/rashi), not degrees. Western aspects are angular: a trine is 120° give or take an orb of a few degrees. Jyotish drishti asks which sign, counted inclusively. Every graha aspects the seventh sign from itself, whatever the exact degrees.
Second, three grahas have special aspects in addition to the seventh:
Only Jupiter's pair is symmetric around the seventh. Mars and Saturn are lopsided, and there is no tidy geometric story that produces all three. What the three do have in common is that Mars, Jupiter and Saturn are exactly the superior planets among the classical seven — the ones whose orbits lie outside Earth's, and which can therefore be seen at any angular distance from the Sun, including opposition.
A separate scheme, rashi drishti, has signs aspect signs by mode rather than grahas aspecting places. It is used in Jaimini methods and is worth knowing exists so it is not confused with graha drishti above.
For a beginner: read the seventh-sign aspect for every graha first, add the three special aspects second, and treat everything else as later refinement.