Define hold

Hold is the scoring method where a player keeps control: you Hold when you maintain Control of a battlefield you have not yet scored this turn, during your Beginning Phase (Rule 469.2). It's the passive counterpart to Conquer — Conquer is gaining Control of a battlefield you didn't control; Hold is still controlling one when your turn begins.

When you Hold, you gain up to 1 point (subject to the Final Point restrictions that apply only to Conquer, Rule 471.1.a.1), and any "when I hold / when you hold" abilities trigger at the battlefield that was Held (Rule 471.2.b) — these are Hold Effects and go on the Chain as Pending Items. Hold happens as part of the Beginning phase of your turn.

One limit matters in practice: you can only score each battlefield once per turn, so a battlefield you already Conquered this turn can't also be Held for a second point (Rule 470).