An assemblage may be the act of assembling or the state of being assembled. More interestingly, however, an assemblage is a set of parts that go together, either parts designed to fit together or random pieces assembled in a work of art.
Words on -age are almost always beautiful; this is a lovely suffix in and of itself. The combination of the sonorants M and L with the breezy S sound makes assemblage a lovely word. This is the noun from the verb assemble. It has a less appealing sister, assembly, whose meaning is more restricted, referring only to an assemblage of people.
Like its sister, assembly, this word may refer to people: "Leslie's parties were always an assemblage of the most enlightened people in town." However, unlike assembly, it may refer to anything has been assembled from different parts: "The bouquet was an assemblage of dried desert flowers Leslie's friend in Nevada had sent her."
This lovely word came to English from Old French assembler "to assemble," a reduction of Vulgar Latin assimulare. This verb comprises the preposition ad "(up) to" + simul "at the same time, together" + a verbal suffix. Simul is based on the primitive root sem- "one, together," which also shows up in simultaneous. The same root also appears in many Indo-European words meaning "same," including same itself. In Greek, however, where an initial S often changes to H, the word for "same" is homos, which is found in many borrowed words in English, including homogenize, homonym, and homotropic.