There are many, many options for other types of email accounts, like Yahoo Mail, Hotmail, Live.com, Outlook.com, AOL mail, your ISP's email service, your company's email service, your domain registrar's email service, etc.
All Android devices need to have a Gmail account in order to use the Google Play store, etc. But you don't actually have to use it for email, etc. As far as the actual email service(s) that you use, that's totally up to you. They each have pros and cons. I use both Gmail and Hotmail on my devices for mail, but I don't use Gmail for my contacts because of Google's privacy policy.
Gmail (and all IMAP-protocol-based mail services) allow you to sync mail across multiple devices. POP-protocol-based mail services do not synchronize across multiple devices, so I would stay away from such (antiquated) POP services. With Gmail (and some other IMAP mail services) you can also sync your calendar and contacts. The Microsoft-based email services (Hotmail, Live.com, Outlook.com, MSN.com, Exchange Servers) use a MAPI-protocol which also enables you to sync mail, calendar, and contacts across all devices, and it integrates with the popular (email/calendar/contacts) PIM program for PCs & Macs known as Outlook.
FYI: Google has said that it uses your contact information and the information contained in your emails to target you and your contacts with ads. Microsoft has said that they won't do that.