How to Teach Toddlers about Emotions?
“Do you have advice on how to teach toddlers feelings and emotions in a way that they can understand?”

Your question is really important because emotional competence is a key skill for children to develop. There is plenty of research showing that children who are emotionally competent tend to do better in life.
A very important way in which children learn about it is by watching us. Children learn more from what we do than from what we say. So, if you want your child to manage his emotions effectively, he must watch you manage them that way. You child is more likely to keep calm under stressful situations if you are calm. If you totally lose your cool, he will also be more likely to lose it.
In general, it is a good idea to validate their emotions (e.g., “I can see you are upset”) but do not amplify them. The idea is to say something like: “I know you are upset, let’s see what we can do about it”, instead of: “I see you are upset, and you are right because this is horrible”). Do not belittle or ridicule their emotions (e.g., “Don’t be silly, there is no reason to cry”). Always praise him when he regulates his emotions well (e.g., “Look how welk you have done. You were angry with your sister but you managed not to hit her”). Children are more likely to repeat those behaviours that we reinforce.
The idea is that you teach your child the tools to manage whatever emotion he feels. The message is: whatever you feel it is OK (there are no right or wrong emotions), and you must express those emotions in a way that is appropriate (e.g., if you feel angry you can say it but you cannot hit).
Finally, remember that the idea is not for your child to avoid any uncomfortable emotions because under certain situations, like a new playdate, they are meant to feel some anxiety. The idea is for him to learn to manage whatever emotions he experiences in an effective manner.
Here are a few more articles you may find helpful:
My 3-Year-Old Meltdowns over Everything
Why my Toddler Says No to Everything?
Tips on Toddler Aggression: When to Worry?
Fostering Emotional Intelligence in Children: A Guide for Parents
I hope this information helps.
Love,
Ana