For the religious term, please see prophet.
Profit was the gain from a sale minus what was invested to make that sale, usually in terms of currency. For example, if one purchased an item for 100 credits, and sold it for 200, then one has gained 100 credits in profit. A profit margin was a measurement of profitability.
Harry Mudd once visited the planet Omega Cygni, where he made a large profit by selling the natives their own oceans. (TAS: "Mudd's Passion")
The archaeologist Vash always chose profit when it came to choose between science and profit. (DS9: "Q-Less")
Profit is also widely known to be the central driving force behind what most capitalistic Ferengi do, and a major aspect of their religion. (DS9: "Body Parts")