What is the difference b/w MYSQL and PostregreSQL

They're both RDBMS' just different ones. There are some commands that change between the two and some differences in the architecture. MySQL is more popular in industry but Postgres is the more popular open source alternative. MySQL can be faster (depending on which version you're implementing) but Postgres is generally considered more extensible.

here you go: https://dev.to/dmfay/the-ultimate-postgres-vs-mysql-blog-post-1l5f