¡Buena pregunta, @mmoderwell! English has one main past tense; Spanish splits it in two. Here's the map.

Preterite vs. Imperfect: The Spanish Past Tenses

The core idea

• Preterite (pretérito indefinido) = completed events. The "what happened" tense. → I walked, it happened, she said.

• Imperfect (imperfecto) = background, habitual action, ongoing states. The "what was going on / used to happen" tense. → I used to walk, it was raining, we were talking.

A classic framing: the imperfect is the video (setting, ongoing scene), the preterite is the photo flash (a discrete event interrupting or advancing it).

Caminaba por el Retiro cuando mi teléfono sonó. "I was walking through the Retiro when my phone rang." Caminaba = scene in progress (imperfect). Sonó = the event (preterite).

Conjugations

Regular -ar verbs (hablar)

⚠️ hablamos and hablabamos-looking forms overlap: preterite nosotros hablamos = "we spoke"; imperfect nosotros hablábamos = "we were speaking" (note the accent).

Regular -er / -ir verbs (comer, vivir)

Notice: the imperfect is very regular — only -ar takes -aba, -er/-ir take -ía. The preterite is where the irregulars live.

Key irregular preterites

• ser / ir are identical in preterite: fui, fuiste, fue, fuimos, fuisteis, fueron. Context decides "I was" vs "I went."

• estar → estuve, estuviste, estuvo…

• tener → tuve, tuviste, tuvo… (had/got)

• hacer → hice, hiciste, hizo (note: no accent, unlike hice)

• poder → pude (managed to) — no pude = I couldn't / failed

• decir → dije, dijiste, dijeron (the -j- stem)

• ver → vi, viste, vio

• dar → di, diste, dio

The three imperfect irregulars (memorize these — it's all of them)

• ser → era, eras, era, éramos, erais, eran

• ir → iba, ibas, iba, íbamos, ibais, iban

• ver → veía, veías, veía, veíamos, veíais, veían

When to use which — signal words

Preterite triggers: ayer, anoche, el lunes, la semana pasada, en 2027, de repente, una vez, dos veces Imperfect triggers: siempre, todos los días, cada verano, mientras, generalmente, antes, cuando era niño

Meaning shifts worth knowing

The same verb changes meaning across the two tenses:

Applying it to your Madrid comment

Look at your own sentences — you actually used both correctly without noticing:

• "Sara caminó por el parque" — preterite, a completed event. ✔️

• "Dejó en un templo que fue un regalo" — preterite events. ✔️

• "un templo que era un regalo del gobierno de Egipto" — here imperfect fits better than fue: a timeless background fact about the temple. (fue isn't wrong for a bounded past, but era is the natural choice for descriptions.)

Mini practice (respond in the comments — en español)

Rewrite with the correct tense of the verb in parentheses:

1. Mientras Sara (caminar) por el Retiro, (hablar) de su historia.

2. Todos los días de mi viaje, (desayunar) churros con chocolate.

3. Ayer (ir) al Templo de Debod y (hacer) un frío horrible.

Full conjugation tables if you want a reference: SpanishDict preterite conjugations and imperfect conjugations.