Hungarian has two complete sets of past tense conjugations — one definite, one indefinite. You choose based on whether the object is definite (a specific, known thing) or indefinite (an unspecified thing). In the past tense this becomes natural very quickly:

Láttam egy filmet. — I saw a film. (indefinite — any film, unspecified)
Láttam a filmet. — I saw the film. (definite — a specific film you both know about)

The magic rule: if the sentence has a/az (the) before the object, use the definite conjugation. If it has egy (a/an) or no article at all, use the indefinite. In the past tense, the definite forms are the ones ending in -tam/-tem, -tad/-ted, -ta/-te, -tuk/-tük, -tátok/-étek, -ták/-ték.

The good news: Hungarians will understand you even if you mix them up, and when you get it right — especially outside Budapest with your family — they will be genuinely delighted. It is one of those features that marks a learner as someone who truly studied the language.

You'll notice that many past tense sentences use meg- as a prefix (megvetted, megkaptam, megnézted). This verbal prefix signals that the action is completed — it's roughly equivalent to the English "up" in "eat up" or "drink up". In the past tense, meg- almost always signals a definite, completed action, so it naturally pairs with the definite conjugation.

In questions and negatives, meg- separates from the verb: Megvetted? → Nem vettem meg. (Did you buy it? → I didn't buy it.) This word-order shift is one of the trickiest — but also most satisfying — things to master in Hungarian.