Question [Q] Tmo_2.2.1-3.4.2-107-boot-devtree-ONLY.sbf ??

can anybody tell me what Tmo_2.2.1-3.4.2-107-boot-devtree-ONLY.sbf is for ?
what it contain ?
currently my stock android 2.1 firmware with 2.5.0 bootloder. whenever i want use any froyo rom from nandroid backup it give me boot loop and when flash Tmo_2.2.1-3.4.2-107-boot-devtree-ONLY.sbf froyo boot fine

i want to know why Tmo_2.2.1-3.4.2-107-boot-devtree-ONLY.sbf need to use and what it contain.
LG Optimus G E975