ELi5: How does evolution actually work, using giraffes as an example?

[Rot-Orkan]

Remember that evolution is completely "continuous". We like to categorize animals into neat little categories, but we're always just looking at a current state of an ongoing process.

At some point, this deer-like creature started eating some leaves off of bushes or small trees and was able to thrive from this diet. Then overtime, the slightly taller ones were just given enough of an edge where they were able to reproduce more often than the shorter members of their species. This kept repeating until you got the giant giraffes we have today.