RAM stands for Random Access Memory; it is a form of computer data storage that stores data and code currently being used. EOS RAM is a resource required for dApp developers for their smart contracts to be deployed.
The Buy/Sell RAM page has 2 tabs available;
RAM Receiver - Enter in the username of RAM receiver (ex. easyaccount1)
Buy in EOS or Bytes? - Select metrics for purchasing RAM
Amount of RAM to Buy in EOS - The field below will auto-calculate and show you the equivalent in Bytes (ex. 1 EOS ≈ 11,304 Bytes as of August 9th, 2019)
Bought - Displays how much RAM you've purchased in Bytes/EOS
In Use - Displays how much RAM is in use in Bytes/EOS
Available - Displays how much RAM is available in Bytes/EOS
Amount of RAM to Sell (Bytes) - You can manually enter how much to sell, or select one of the four buttons below to auto-calculate how much RAM to sell in percentages
You can enter a value manually or select one of the buttons below the field to auto-calculate 25, 50, 75 or 100% of the available RAM on your account.