Referring to something that occurred at a point in past time and is finished.

Here the simple past refers to finished events of long duration.

Here we know neither when the action began nor when (or whether) it finished.

Dave climbed on Everest throughout the summer.

Dave used to spend time here and he would often sit in the garden and read.

Dave was climbing Everest when he fell.

Dave was climbing Everest.

Dave went home early.