Jats are the largest landholding community in Punjab and Jat Sikhs are the dominant group in rural Punjab by land, by numbers in most villages, and by political representation. Almost every Chief Minister of Punjab has been one.
The community's origins are argued: pastoralists who settled, an agricultural population that consolidated in the medieval period, or something else. The evidence does not settle it and the claims made about it are usually claims about status.
Large numbers took amrit in the eighteenth century and the Khalsa's leadership from the misl period onward was substantially Jat. That association shaped how the tradition developed and how it is perceived.
The community holds most of Punjab's agricultural land, carries most of its agricultural debt, and provides most of its emigrants and a large share of its soldiers.
It is also the group whose position in the village makes caste in Punjab operate the way it does, which is stated on the caste page on this site and belongs here too.
The Jats are the landholding cultivating community of the Punjab and they are the majority of Sikhs in the state, which is why Punjab's politics, its land and its religious institutions run together.
They are Sikh, Hindu and Muslim across the region, and the got system, the marriage rules and the village structure are shared across all three.
The identification of Sikhism with one community is a fact about the demography rather than about the teaching, and the tension between those two is a permanent feature of Sikh public argument.