Yes, you can purchase the Oyster card at Heathrow.
This will be a "regular" Oyster card; what most visitors to London buy.
The visitor Oyster card is sold online and mailed to you (more expensive)....you don't need to do this because it's so simple to buy the Oyster card once you get to Heathrow or into London.
Depending upon where your hotel is located, you might take the Heathrow Express train into London. If your hotel is near Paddington Station in London, this is a good option.
Oyster cards can be bought at train and tube stations in London, also at small food stores. If you use a machine at Heathrow or inside one the tube stations, it will look like an ATM machine. You use a credit card to pay, choose an amount to put on it (20 to 30 pounds) and then your Oyster card will pop out.
There are dozens of YouTube videos guiding you through the purchase of the Oyster card.
I'm sure others will chime in about this, but you can also tap your credit card or phone to pay for rides on the tube.