These are all transactions that are recorded on-chain.

In short: Is https://blockchain.info/nl/charts/n-transactions-excluding-chains-longer-than-100 the transaction volume? (Purchase real life goods etc)

Assuming that every transaction involving the trading of bitcoin for goods/services is done on-chain and not internally as might be possible by some sites, ( eg all trading on binance, bittrex etc.) then yes.

It certainly indeed does not represent "orders" that you make on exchanges such as bittrex ( to buy X coin or sell Y amount of bitcoin for $), all these transactions are performed internally on their platform, and are never actually recorded on the blockchain, unless you explicitely want to withdraw your "balance" in the form of bitcoins to your wallet. ( which is why you really shouldn't trust them with any of your coins)..