Basically the same as the Titans in Greek mythology. Just like the Titan Gaia, the Jotunn Jord is Earth herself. Likewise the Celtic goddess Danu is the mother of all life and Earth, she's often depicted as the embodiment of nature pregnant, displaying fertility.
All Indo-European pantheons display the same archetype, that is a dual-pantheon system in which a human-like pantheon of gods, that taught us human things like music and art, magic, military prowess, metal smithing, crop techniques defeated an older pantheon of more primitive/primordial gods, that are usually chaotic, and represent the natural forces that humans don't have control over, storms, snow.
This common mythology themes mirror the Indo-European people's own history, in which from their homeland in the Asian steppes of Kazakhstan they invaded/migrated to new lands and spread their domain all across Eurasia and conquered the inhabitants.
There's this misconception in popular culture (thanks to things like Marvel comics) that giants (Jotunn) are exclusively evil and enemies of the gods and humanity, which couldn't be further from the truth.