The generic IFFT OFDM transmitter takes $N$ serial input data symbols, parallelizes them, maps them to their signal constellation points, and processes all $N$ resultant complex values using the IFFT to produce $N$ subcarriers (assuming no virtual carriers).
The IFFT takes $N$ input values and produces $N$ output values, such that changing a single input value will change all output values. Therefore each input symbol contributes to each of the $N$ subcarriers; each symbol is "shredded" across all subcarriers.
However, several sources state that in OFDM "each modulation symbol is mainly confined to a relatively narrow bandwidth" (Communications Engineering Desk Reference, Elsevier, 2009, 1st ed, p.287).
Are these two different OFDM implementations, or is the IFFT implemented in a different way to achieve this?