Lore was the same model and appeared the same as Commander Data, but he was created before Data. He had emotions which were more like organic life forms thanks to an emotion chip, but unlike Data he had no ethical program and was selfish and malevolent. When he noticed that the colonists on Omicron Theta were afraid of him and didn't like him, he made contact with the crystalline entity and had it destroy the colony. Before the entity arrived, the Soongs disassembled Lore.

When Data and the Enterprise crew returned to Omicron Theta, they discovered Lore's parts and reassembled him. After creating trouble on the Enterprise, they sent him away in a shuttle craft. They met up again when Soong was dying and wanted to give Data an emotion chip like Lore's, but Lore stole it. In the end, Lore was deactivated and dismantled after leading a Borg faction against the Enterprise and the Federation. His emotion chip was salvaged and saved by Data.

The Star Trek Project

Sources:
http://www.startrek.com

Lore (?), n. [F. lore, L. lorum thong.] Zool. (a)

The space between the eye and bill, in birds, and the corresponding region in reptiles and fishes.

The anterior portion of the cheeks of insects.

© Webster 1913.

Lore, obs. imp. & p. p. of Lose. [See Lose.]

Lost.

Neither of them she found where she them lore. Spenser.

© Webster 1913.

Lore, n. [OE. lore, lare, AS. lar, fr. lran to teach; akin to D. leer teaching, doctrine, G. lehre, Dan. laere, Sw. lara. See Learn, and cf. Lere, v. t.]

1.

That which is or may be learned or known; the knowledge gained from tradition, books, or experience; often, the whole body of knowledge possessed by a people or class of people, or pertaining to a particular subject; as, the lore of the Egyptians; priestly lore; legal lore; folklore.

Fairfax.

His fair offspring, nursed in princely lore. Milton.

2.

That which is taught; hence, instruction; wisdom; advice; counsel.

Chaucer.

If please ye, listen to my lore. Spenser.

3.

Workmanship.

Spenser.

© Webster 1913.