Does the bitcoin design make bitcoins suitable as a medium of exchange, a store of value, or both? Money is often seen as having various functions, such as "medium of exchange" (something useful for conducting transactions, and "store of value" (something valuable as an investment).

Was bitcoin designed to provide both functions, or just one?  How does it mainly function today?
Today, it primarily serves as a store of value. It is inherently more useful as a medium of exchange, its intended purpose. Perhaps a bit ironically, its expected future usefulness as a medium of exchange is what is driving its present usefulness as a store of value. The thinking is that if you get them now when they're cheap, in the future when they're used as a medium of exchange (and thus there's much more demand) they'll be worth more.