Here are some examples of rules you should follow when sharing online:
There are a few exceptions though. If you are using an app with your teacher and classmates, you can post personal information. Also, when writing an email, you probably should not use abbreviations, especially writing to a teacher or other adult.
One of the reasons to make your password not contain any personal information is that people might guess your password from what you post. For example, say your password was this:
SwimmmingDoggo123
and one of your posts said this:
'Hi, nice to meet you @fancyflamingo! I have a dog named Woofers and he really likes to swim in our pool. Do you have any pets?'
If fancyflamingo or someone else who might want your password read that post, they might try your password based on what you told them. It's still OK to tell someone you have a dog who likes to swim, but it's not a good idea to put that in your password.
If someone sends you a personality test online, and you take it and send back the results, they know so much more about you! Let's say a social media site had you take a personality test so they can recommend some online friends. They might use that information in bad ways like selling it or good ways like reccomending online friends with similar results. To actually know what they do with it, you probably will have to read the privacy policy.
Yes, you do! When you go onto a website, the website can gather all sorts of information about you. The combination of all of that information is called a 'digital fingerprint' and it can be used to track which websites you visit. To see what types of information a website can gather about you, look at my evil password generator.