Ektachrome, Kodachrome, etc. are registered trademarks of Kodak - they are used for different products. Ektachrome film is generally slightly different from Kodachrome, by virtue of a different photo-sensitive emulsion (the component applied to the clear "carrier" film which is the bulk of what we look at when we see the bit that is rolled up inside the usual cartridge), and they can be either negative or alternatively "reversible" stock (i.e. suitable for making "positives" which is what slides come from). Negative stock is developed in total darkness and permanently fixed (so it will not change on exposure to daylight) whereas reversible stock is developed, then briefly exposed to light for a given time, before being developed further (in darkness) and then fixed. The latter shows a positive image, as opposed to the more familiar negatives. The vast majority of cine films are shot on Ektachrome stock and are reversed into positives to be suitable for projection. For more detail you can perhaps find a source in your local library or else on the Net.