With ancient Greek coins, they used the Drachma (Spelt as Drachm on Numista). As Greece wasn't truly unified in the sense it is today, it existed more as a collective of city-states with a shared currency. Each city state minted it's own “personal” drachmae, although they were usually accepted throughout Greece.
Functioning in a somewhat similar way to the Euro & the EU does today; independent nations with a shared currency. Obviously a huge simplification, but it works well enough as a “flavour” of what it was like.
The shared currency was the Drachmae which itself had a range of different coins including but not limited to obols (Smaller denominations) and tetradrachm (larger currencies). In this example, 6 obols = 1 Drachmae. 4 Drachmae = 1 Tetredrachm.
You can read some more detail here on the wikipedia page: en.wikipedia.org/wiki/Ancient_drachma
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In terms of identifying your specific coin, we're going to need a few more details. Ideally, the diameter in mm. That should narrow the catalogue down a lot. It'll also narrow down the coin options - Tetradrachm are usually 25-35mm depending on the city state.
The motif of the chariot turns up quite often, as does dolphins. But combining size & motif should really thin it out.
It's also possible that your coin may not exist on Numista (the catalogue isn't exhaustive - so many hundreds of variations), or that your coin is a modern reproduction. Sadly, I'm not well versed enough in ancient coins to make the real/reproduction call.
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Still, I hope that gives you some starter information as to what you're looking for.
