Unless you are using a corporate email system, your email provider will very likely use either IMAP or [much older] POP3 email protocols to access your email. Deleting an email account from your iPad will only affect services associated with that specific account.
In addition to email, some email providers support synchronisation of Contacts, Calendars and Notes along with basic email account - making this data accessible using a web browser (from any computer) via the email providers webmail platform. You can see precisely which additional services are associated with any specific email account from iPad settings:
Settings > Mail > Accounts > [your email account]

In the above screenshot, for this specific email account, you can see that Mail, Contacts, Calendar and Notes can be synchronised with the mail-providers platform - but in this example, only mail has been enabled.
Below the selection options, you’ll see the Delete Account button. Deleting the account will delete all data associated with the mail account from your device - but will not, of itself, delete the email and associated additional data from the mail-providers server infrastructure.