What is Bitcoin Core? That's one currency they are selling. Is Bitcoin Core just Bitcoin?
This is exactly why you shouldn't use that site, they try to make a new name for Bitcoin, and try to trick/scam people into thinking they buy Bitcoin when they sell and promote their own Forkcoin Bitcoin Cash.
This had led to many new users sending their coins on the wrong chain, and losing access
To buy Bitcoin, user a reputable exchange.
And in case you're wondering, OP. Plenty of people have already been misled into making that mistake. I've come across several threads already with people buying from bitcoin.com and realising later on, they've actually bought the altcoin Bitcoin Cash.
Tell you what: get an account on localbitcoins.com. Look for a reputable trader (>500 trades, 100% good/neutral feedback). Use only an online trade. Everything is escrowed so as soon as you've made your payment and the trader (seller) gets your funds, escrow is released and you can withdraw Bitcoin to your own wallet.
There are many, many other ways to get Bitcoin and many reputable services. But this is always the platform I recommend to first-time buyers. Just to give you the confidence of escrow protection (and get your first taste of p2p!).