The main Schools of Tibetan Buddhism are: Nyingma, Kagyu, Sakya, and Gelukpa

The Dalai Lama who is Gelukpa  is considered sort of like the "Pope" of all Tibetan Buddhists and to some degree the leader of all Buddhists on earth by some people. So, the Dalai Lama is very much like the Pope is to all Christians on earth.

The Dalai Lama's lineage is a more recent lineage and more Intellectual and structured in some ways than the more ancient ones. The Most ancient lineages are first Nyingma and next Kagyu which began with Marpa the Translator and Milarepa.

The First Dalai Lama was born in 1391 AD.