What is attributed to him
Ancient sources name Iktinos as an architect of the Parthenon, working with Kallikrates, and Plutarch's life of Pericles lists him among those directing the building programme. He is also credited with the temple of Apollo at Bassae and with work at Eleusis, and is said to have written a treatise on the Parthenon with Karpion. The treatise is lost.
Every one of those attributions comes from later literary report. No inscription names him on the building, and the Parthenon's own building accounts, which survive in part and record payments in detail, do not supply an architect's name in the way a modern reader would expect.
What that means
The Parthenon is one of the best-documented ancient constructions and its architect is one of the least documented ancient people. That gap is characteristic rather than exceptional: Greek building accounts record tasks and payments rather than authorship, because the categories the inscriptions use are not the categories a modern architectural history wants.
The division of responsibility between Iktinos, Kallikrates and Phidias, who directed the sculpture, is not recoverable from the evidence.
Bassae
The temple of Apollo Epikourios at Bassae in Arcadia, attributed to him by Pausanias, is a strange and interesting building — unusual in orientation, mixing the orders, and containing what may be the earliest Corinthian capital known. Whether the attribution is correct is not established.
Why the platform records him
Because he is the standard case of what ancient architectural authorship looks like: a name transmitted by literature, attached to buildings that carry no signature, in a tradition that did not record designers the way it recorded dedicators.