Similarity has to do with when two or more things are viewed, then the identical or alike thing between them are showed.
When two things are compared, and there exists a difference, then it means that the things are dissimilar.
Since your question is vague, now you know their meaning. What is left to know is how to identify them using examples.
For example,
Read more here:
https://brainly.com/question/10426996