Gmail alias generator is a tool that allows you to create temporary email addresses that you can use to protect your privacy and avoid spam.
You can generate an alias and use it to sign up for a service or website. So you can receive all emails necessary for the sign up process. Once you are done, you can simply find all emails received to the alias. You can also create a filter, which will prevent you from receiving all emails sended to this alias.
Some people think, that they can use their main GMail address during the signup process and unsubscribe later. But this is not a good idea. You will receive a lot of spam and your inbox will be full of unnecessary emails. Those emails will be hard to filter out. Some services do not provide a function to unsubscribe from all emails. Websites could split their emails by themes. It could be different advertising subjects, website feature related notifications and so on. That's why people have to unsubscribe multiple times from every single website.
Some websites also sell your email address to third parties. Nobody really reads all the privacy policies, terms and conditions for all websites they sign up. So the website owners could have a right to sell those email addresses to anyone. That's why those users will receive lots of emails from different spammers and will have to keep unsubscribing from them over and over again.
But people can use email aliases, to filter such emails by the reciever address. For example, if the GMail user has an example@gmail.com address, they can simply create an alias for it. It could be something like example+nospam@gmail.com. The user could use this address to sign up on a suspicious website. All emails that sent to the alias address will be received to the main GMail INBOX folder. The only difference is the receiver address, which will be the exact example+nospam@gmail.com address, if the message was received from that suspicious website. That's why the user can simply create a filter, or even remove all emails recieved to that alias.
Moreover, such aliases are great for checking who is selling your data to the third parties. For example, you create an alias example+for-spammer@gmail.com to sign up on the spammer.com website. But later you receive an email from the other-spammer.com, which uses the same alias. That means, that the spammer.com website sold your email address to the other-spammer.com.
Gmail generator is a great tool to keep your INBOX clean from spammers. But as any other tools it has not only advantages but also disadvantages.