A variation in chess is a specific, named sequence of moves that branches off from an opening, defining one particular path among all the possible continuations available in the early phase of a game.
Every opening splits into multiple variations, which themselves break down into sub-variations. For example, within the Sicilian Defense, the Dragon Variation refers to the moves 1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 g6 — a precise path with its own strategic plans, typical traps, and deep theory. Choosing a variation means committing to a territory whose key ideas can be studied and internalized.
In practice, memorizing everything is neither necessary nor realistic. At this level, the priority is understanding the purpose behind each move in your main variation: why a particular pawn advances, why a knight heads to that square, what weakness the opponent is creating. Mastering two or three solid variations with both White and Black will allow you to reach the middlegame in familiar positions with a clear plan in mind.