Every Russian verb comes as a pair. The imperfective describes an action in progress or repeated; the perfective describes one completed whole. In the past, читал means I was reading and прочитал means I read it through to the end.
Examples
- В прошлые выходные я осмотрел весь музей.
- Last weekend I went round the whole museum.
- Вчера я осматривал музей три часа.
- Yesterday I was going round the museum for three hours.
- Я написала письмо и отправила его.
- I wrote the letter and sent it.
The mistake to avoid
A perfective verb has no present tense - напишу is future, not now.
Where this fits in
Talking about the past, Russian A2: Tell stories about yesterday, last weekend, and life experiences using the past tense. Russian past tense is gendered — verbs change form for masculine/feminine speakers.