These verses are attributed to Atisa, an Indian Buddhist pandit
who travelled to Tibet
in the 12th Century and there established the Kadam ("Virtue") school.
While the Kadampa died out soon afterwards, its influence continued through Gampopa, one of the founders of some of the Kagyu schools and through the later revival of its core Teachings by Tsongkhapa, whose heirs founded the Gelug school.
"Lojong" or "mind-training" in this context means turning one's habits of cognition, perception, and behaviour from one based in self-concern to a recognition of the reality of suffering for oneself and others and the resolve to liberate oneself and others from the causes of suffering.
"Suffering" in this sense is a poor translation of "dukkha", a Sanskrit term, the roots of which mean "obstruction". One is "obstructed" through commitment to a conditioned and closed approach to experience ("samsara": "the circuit of conditioning").
Lojong is intended to be a foundational set of Mahayana contemplations, based on the Bodhisattvacaryavatra.