The past simple (aorist): ку́пих, видя́х

The aorist is the main past tense: finished actions, one after another — "⁠Вчера отидох на пазара и купих ябълки.⁠" — Yesterday I went to the market and bought apples.

The usual pattern is:

• аз -х, ни́е -хме, ви́е -хте, те -ха
• ти / той / тя — no ending

The vowel before them depends on the verb: "⁠чакам → чаках⁠", "⁠работя → работих⁠", "⁠видя → видях⁠", "⁠дойда → дойдох⁠".

Watch out:

• The "⁠ти⁠" and "⁠той⁠" forms often look like the present: "⁠Той работи.⁠" — context tells you which. Sometimes only the stress differs: "⁠чете⁠" (is reading) / "⁠чете⁠" (read, past).
• Irregular classics: "⁠съм → бях⁠", "⁠ям → ядох⁠", "⁠пиша → писах⁠", "⁠мога → можах⁠", "⁠дам → дадох⁠".

Most aorists come from perfective verbs: "⁠купих⁠", "⁠казах⁠", "⁠взех⁠".

For speakers of your language

The aorist ≈ English past simple ("⁠I bought⁠"). The difference: the ending changes for every person.