This is the 75th most frequent French word.
selon
According to; depending on.
Here, 'selon' is used to indicate 'depending on' a condition or factor that affects the outcome.
Le menu change selon les saisons.
The menu changes according to the seasons.
In this sentence, 'selon' refers to tailoring something based on somebody's preferences or choices.
Selon vos préférences, nous pouvons varier l'itinéraire.
According to your preferences, we can vary the itinerary.
The word 'selon' is used here to mean 'according to' someone else's opinion or statement.