Individual plans do not let you share your account with others. Others can only view the data you scraped. They can not update the data or add/edit new functions to your spreadsheets.
Business plans introduce collaboration features. As long as you are the spreadsheet owner, your colleagues can refresh the IMPORTFROMWEB() functions, as well as add and edit new functions. Requests are counted under the account owner.
Enterprise plans are made for companies that need multiple users. Each user has his own account that can be tailored upon his needs.