Familiar shapes in familiar surroundings are invisible. We do not usually see words, we read them, which is to say we look through them at their significance, their contents. Concrete poetry is first of all a revolt against this transparency of the word — as is all poetry. I hardly need to quote "A poem should not mean but be" and all the similar statements. But there is a difference. While poetry in general uses the material aspects of the word as functional in the "poetic information" process in poems about whatever subject ("The sound must seem an echo to the sense"), concrete poetry makes the sound and shape of words its explicit field of investigation. Concrete poetry is about words. Further, it stresses the visual side which is neglected even in the 'sound and sense' awareness of ordinary poetry (as well as in the oral bias of most linguists).
This does not mean that concrete poets want to divorce the physical aspects of the word from its meaning — which would be a most difficult thing to do. Words are not colors or lines: their semantic dimension is an integral part of them. In order to destroy meaning you would also have to destroy the word as a physical object: you would have to atomize it into letters, fragments — or go to a language you do not understand. To judge by the name "Noigandres," which the Brazilians Augusto and Haroldo de Campos and Décio Pignatari chose for their group, they seemed to intend exactly that. The name is taken from Pound's "Canto XX" where the old Provencal scholar Lévy says:
You know for seex mon's of my life