"Why don't you talk much?"
"Do you even have anything to say?"
"She's just in her own world."
As someone who classifies them self as both shy and slightly introverted, I have heard it all.
To me, being shy means overthinking the small situations, worrying about others' opinions, and holding back from expressing myself. Shyness is often seen as a mild or beginning form of social anxiety and these people tend to stay away from scenarios where others can judge or evaluate them in any way, even if it is positive.
On the other hand, being introverted simply means that you prefer quiet time with yourself. Over-stimulation is a key factor to introverts, if they are in an environment with many people, such as parties, clubs, or festivals, they can still enjoy it, but may need time to be alone and regain energy.
To me, the beginning of a new year or semester represents fear stemming from the idea of having to introduce yourself in front of the class and/or play "ice-breakers". Many times, I stress and replay what I am going to say about myself in my mind and do not even hear what others are saying about themselves. When the time comes for me to introduce myself, everything that has been repeated over and over again in my mind disappears. A complete blank slate usually resulting in stutters and shakes as I try to remember what the professor is wanting me to answer. In my mind, an introverted person would have little to no problem answering these questions and pass it off as another routine way to start the class and meet others.
If you're still confused, consider this:
A teacher wants to begin an activity, but two children do not want to take part in it. One child would rather stay at their desk and read, whereas the other thinks about joining, but is too afraid.
The first child is an introvert, wanting to be alone because group activities stress them out. The other child is shy, they think about joining, but the factor that stops them is possible judgement from others.
It is possible to overcome shyness through therapy, but not for introversion. Trying to turn an introvert into an extravert has the possibility to cause more stress and lead to self-esteem issues. These people can learn of strategies to deal with introversion, but cannot change who they are.
While being shy and/or introverted is often seen as negative, that is not the case at all. This just means that social situations are an extreme turn off, which is normal for many. People who have these traits often feel that something is wrong with them, or that they need to get help. This solely depends on the individual and what they feel would be helpful for them. Many seek therapy to have someone to talk to about feelings, insecurities, and worries. Although it may seem scary, it helps to always know that no matter what situation you are in, you are not alone.