Tib., sgrub brgyud brgyad
The term Practice Lineage in itself (Tib., sgrub brgyud), leaving out the qualification eight (brgyad) for a moment, is an important and interesting one. The Practice Lineage concept does not discriminate between schools or orders according to the well known scheme of the so-called "four schools" (Nyingma, Kagyud, Gelug and Sakya), nor is it based on a given school’s historical roots (i.e. first diffusion Old School or second diffusion New Schools).
What it does refer to is a much more essential point, namely the question of whether or not the emphasis is on personal experience of the teachings or mainly on scholarly knowledge. Schools of the Practice Lineage put emphasis on experience, whereas schools that encourage emphasis on expounding the scriptures is known as the Scholastic Lineage (Tib., bshad brgyud).
In a sense, these two streams correspond very well with the in-depth analysis of Tibetan Tantric Buddhism published by Geoffrey Samuel. In his book Civilized Shamans, Samuel discriminates between shamanic and monastic teachings and techniques; and although these two streams have continuously intermingled, this terminology does fit the Tibetan concepts of sgrub brgyud and bshad brgyud.
In yet another sense - but certainly not in any easyly discernable black and white fashion - the experiental, shamanic, mystic stream often coincides with teachings that nurture individuality (including non-celibate lifestyles and secret practices in the tradition of Indian vamacara); whereas the scholastic, monastic stream is the more orthodox, 'virtue' oriented, celibate and ascetic one (somewhat corresponding to Indian dakshinacara).
Rests us to look at the list of schools known as Eight Practice Lineages and/or Eight Great Chariots of Spiritual Accomplishment (Tib., sgrub brgyud shing rta chen po brgyad):