Learn English – Do you come? Are you coming

I see a bus come.

I see a bus coming.

When you say I see a bus come, it means the bus has already come, and now stopped at the stand. When you say I see a bus coming, it means the bus is on its way to the stop, progressing.

1. We saw Kim leave the bank.

2. We saw Kim leaving the bank.

Slight as it is, there is a difference in meaning between those sentences.

In sentence #1, we saw the whole event of Kim's leaving the bank, while in sentence #2, we saw a segment of it. Sentence #2 has a progressive meaning in it. The contrast is same as that between Kim left the bank and Kim was leaving the bank.

_{From - CGEL page no. 1237}

Some other example sentences might be helpful -

3. I saw him play.

4. I saw him playing.

In sentence #3, it is meant that I saw his playing throughout the match, while in sentence #2, it meant that I saw his playing for sometime during the match. Something like that.

We would say, "how long have you lived there?" (present perfect; began in the past and continues)

Or, "how long has your family lived there?"

We might say "How many years have you lived here?" if the precise number of years were critically important, e.g., you are eligible for some benefit after living in a place for three years. But usually "how long" is the better option.