To think in a chronological way means to order facts or events based on the time they occured. Most of times this is done placing the ones that happened first in the beggining and the most recent ones at the end. We have developed a reasoning based on this type of structure, when you tell someone a story or about your life you usually start from the origin and continue until the most recent events.
Timelines use the same process, as they are sequences of events placed in chronological order. Rememeber when you learned about human evolution, a line showing the year illustrated when the different types of human ancestors lived. That was a timeline.
We can see they both relate as we understand time as a series of events happening in a line beggining in the past and continuing until the present. Chronological thinking implies making a timeline in your head to undestand reality, a timeline is a graphic representation of that.
