Question

-ir and -er ending verbs are very similar in their endings when they are conjugated. How do they differ in their endings when they are conjugated? Don't make it too advanced.

Answer 1

Short answer: in most tenses -er and -ir verbs use the same endings. The main visible difference is in the present (indicative) nosotros and vosotros forms.

Present indicative endings
- -er: o, es, e, emos, éis, en
- -ir: o, es, e, imos, ís, en

Examples
- comer (‑er): como, comes, come, comemos, coméis, comen
- vivir (‑ir): vivo, vives, vive, vivimos, vivís, viven

Other common tenses where they are the same
- Preterite: í, iste, ió, imos, isteis, ieron (comí / viví, etc.)
- Imperfect: ía, ías, ía, íamos, íais, ían (comía / vivía, etc.)
- Present participle: ‑iendo (comiendo, viviendo)
- Past participle: ‑ido (comido, vivido)
- Future and conditional endings are the same for both, and present subjunctive endings match as well.

Note (brief): some irregular/stem‑changing ‑ir verbs behave differently in certain forms (they can change in the nosotros form where ‑er verbs often do not), but that’s a more advanced detail.