If I delete an email on my iPad does it delete the email from my computer?

That depends. If the email account is an IMAP account, then yes. The whole point of IMAP is your Mail actually stays on the server, not the device. IMAP keeps all devices up to date with the sate of mail (so you don't see the same unread or new message umpteen times on different devices). So when you delete on one device, you delete on all. However, most IMAP accounts have a trash folder on the server as well, that syncs to all devices. Your mail typically is not really gone until you empty the trash folder (which you should do occasionally as that trash folder does count against your account's storage limits).

If your email account is a POP account, the mail is actually downloaded to the reading device, and instantly deleted from the server once downloaded. POP accounts typically do not store any mail on the mail server and all mail is downloaded to the first device that reads it. Some POP accounts will allow you to change a setting to "keep mail in server" so other devices will also see it each message as new mail as well. If doing that, you are limited in that most POP account's have very limited mail storage so cannot keep a lot of mail on the server. And changes you make to emails are local to each device, not global across all devices.