Use is when the subject is a singular noun or a third person singular pronoun (he, she or it).
- Shiva is my friend.
- He is an archeologist.
- Uma is an eminent pediatrician. She works at a private hospital.
- The elephant is the biggest animal on land.
- The baby is crying. It is hungry.
Use are when the subject is a plural noun or a plural pronoun like you, we and they.
- You are the most wonderful person I have met.
- They are working on an important project.
- We are still waiting to hear from them.
- The children are busy with their studies.
- These mangoes are very sweet.
- Those memories are painful.
Use am when the subject is the first person pronoun I.
- I am writing.
- I am working.