• for repetitive or constant actions that began in the past and continue to the present

• for actions that happened at an unknown or unspecific time in the past

I have loved cats since I was a child.

Steph has visited Wales three times.

• for actions that began or occurred before another time in the past

She had just crossed the street when the runaway car crashed into the building.

• for actions that will be completed before or at a specific future time

By the end of this year, I will have seen three concerts.