They are users you do not follow, users you do not follow, users with the default profile photo, users who have not confirmed their emails, and users with unconfirmed mobile numbers. You have the option of blocking or allowing.

• To do so, go to your account’s settings >> notifications and advanced filters. There is the previously mentioned list of groups with checkboxes to check or uncheck ( unchecked by default ).
• You can also use the old notification filter option that Twitter used to have, which was quality filter. The quality filter reduces spam on your notification timeline automatically. As soon as you turn it on, it uses your app’s data usage to determine which notifications you receive or do not receive.

• Using it in conjunction with the advanced filters we’ll discuss later narrows the types of notifications you receive for your security and peace of mind.
• When you get to the advanced filters section, you must check and uncheck the boxes to suit your privacy needs. Check the images below:

• Then there are what Twitter refers to as “muted words.” This feature will not block any accounts or words, but you are telling Twitter that you do not want to see anything about that name, word, username, hashtag, or anything else on your home timeline or notification timeline from anyone or anyone you do not follow for however long. (You’ll have to do that.) Look at the image below.