"Enriching" uranium means increasing the proportion of the uranium-235 isotope to other isotopes. Uranium-235 is preferred for sustaining the chain reactions required for nuclear energy.

A simple nuclear power plant may require uranium enrichment levels of around 3-5%. A nuclear weapon requires upwards of 80-90%.

Iran has stockpiles of 60%-enriched uranium, far, far beyond civilian nuclear fuel levels. There is _no way_ they aren't trying to develop nukes.